Piezoelectric pump and fluid transferring system

ABSTRACT

To provide a piezoelectric pump including: a structure including a piezoelectric element and a support member that supports the piezoelectric element; and a first substrate and a second substrate that sandwich the structure, wherein the piezoelectric pump has: a pump chamber surrounded by the second substrate and the structure; and a first opening and a second opening that are communicated with the pump chamber, and wherein a space is provided so that the structure flexes in a direction opposite to the pump chamber according to an operation of the piezoelectric element.

FIELD OF THE INVENTION

The present invention relates to a piezoelectric pump and a fluid transferring system.

BACKGROUND OF THE INVENTION

Various micropumps for transferring a very small amount of fluid are conventionally studied. A piezoelectric pump that includes a piezoelectric element as an actuator is proposed as one form of such micropumps. For example, Japanese Patent Application Laid-Open No. H10-299659 proposes a piezoelectric pump in which a piezoelectric element is disposed outside a silicon substrate (Si substrate) forming a flow path of a fluid, for the purpose of providing a micropump that can always produce a constant discharge regardless of a change in external pressure and also achieve bidirectional feeding. The document contends that, since this piezoelectric pump uses a unimorph structure of the piezoelectric element and the silicon substrate which functions as a diaphragm, the piezoelectric pump can be manufactured very thin.

Moreover, Japanese Patent Application Laid-Open No. 2007-32408 proposes the following peristaltic piezoelectric micropump for the purpose of providing, by a simple construction and manufacturing method, a compact peristaltic piezoelectric micropump or the like that has a large discharge pressure and a small change in transferring amount with a change in an external environment. This peristaltic piezoelectric micropump includes: a first platelike body in which an inlet port and an outlet port of a fluid are formed; a second platelike body made of an insulating material and disposed on a side of the first platelike body in tight contact so as to block the inlet port and the outlet port; a piezoelectric element provided, via a common electrode, on a side of the second platelike body opposite to the first platelike body so as to correspond to an area between the inlet port and the outlet port; and a plurality of driving electrodes arranged between the inlet port and the outlet port on a side of the piezoelectric element opposite to the second platelike body. Applying a voltage sequentially to the plurality of driving electrodes causes the second platelike body to perform a pumping operation. The document contends that, in this peristaltic piezoelectric micropump, a pumping operation is carried out between the substrates by applying a predetermined voltage sequentially to the plurality of driving electrodes, so that a fluid can be transferred while suppressing backflow without using a valve.

SUMMARY OF THE INVENTION

However, as a result of conducting a close investigation of the conventional piezoelectric pump proposed in Japanese Patent Application Laid-Open No. H10-299659 described above, the inventors of the present invention found that such a conventional piezoelectric pump propagates the vibration of the piezoelectric element to outside the piezoelectric pump. When using the piezoelectric pump which propagates the vibration to outside, in the case where other elements are integrated together with this piezoelectric pump at high density, the other elements are affected by the vibration. Therefore, such high-density integration is difficult. Besides, in the case of using a component having a poor vibration resistance together with this piezoelectric pump, the component having the poor vibration resistance is still affected by the vibration even when the piezoelectric pump and the component are separated from each other, so that the combined use of the piezoelectric pump and the component is difficult. The inventors of the present invention further found that such a conventional piezoelectric pump has a difficulty in stably transferring a fluid by a constant flow amount. Especially when making a compact or thin piezoelectric pump, it is difficult to accurately manufacture a piezoelectric pump that is capable of stable fluid transfer. Hence there is a growing demand for such a capability (transfer stability).

Furthermore, as a result of conducting a close investigation of the conventional piezoelectric pump proposed in Japanese Patent Application Laid-Open No. 2007-32408 described above, the inventors of the present invention found that, in such a conventional piezoelectric pump where the plurality of driving electrodes cut separately from each other are arranged on the side of the piezoelectric element, these driving electrodes easily peel away, and warpage in the piezoelectric element can occur. In addition, when a plurality of driving electrodes are provided on one piezoelectric element, a stable operation is difficult especially in high speed driving, and a variation in displacement amount tends to occur. Moreover, while the displacement of the piezoelectric body increases in a central part in an in-plane direction of the driving electrodes, the displacement becomes smaller with a distance from the central part. An area where the displacement is small will end up being the so-called dead space, and the fluid flowing in this area tends to remain there. As a result, in the piezoelectric pump as a whole, the voltage applied to the driving electrodes cannot be efficiently converted to the fluid transferring capability of the pump.

The present invention was conceived in view of the above-mentioned circumstances, and has a first object of providing a piezoelectric pump and a fluid transferring system that adequately suppress propagation of a vibration by a piezoelectric element to outside.

Moreover, the present invention has a second object of providing a piezoelectric pump that adequately prevents electrodes included in a piezoelectric element from peeling, performs a sufficiently stable operation even in high speed driving, and adequately suppresses a variation in displacement amount.

Furthermore, the present invention has a third object of providing a piezoelectric pump that can transfer a fluid with sufficient stability.

As a result of conducting intense study for achieving the first object stated above, the inventors of the present invention found that the direct propagation of the vibration of the piezoelectric element in operation to outside is caused by providing the piezoelectric element in the piezoelectric pump in a state of being exposed to outside. The inventors of the present invention then discovered that the propagation of the vibration to outside can be adequately suppressed by providing the piezoelectric element in the piezoelectric pump so as not to be exposed to outside, and completed the present invention as a result of further conducting detailed study.

As a result of conducting intense study for achieving the second object stated above, the inventors of the present invention found that the driving electrodes easily peel away because, when the piezoelectric element increases in size with respect to the driving electrodes, a range of bend of the driving electrodes with the displacement of the piezoelectric element increases. The inventors of the present invention also discovered that, when a plurality of driving electrodes are provided on one piezoelectric element, a voltage applied via one driving electrode affects the displacement of the piezoelectric element corresponding to its adjacent driving electrode, which makes a stable operation in high speed driving difficult or induces a variation in displacement amount. The inventors of the present invention then found that the second object stated above can be achieved by eliminating these factors, and completed the present invention.

As a result of conducting intense study for achieving the third object stated above, the inventors of the present invention discovered that the conventional piezoelectric pumps cannot transfer a fluid stably for the following reason. That is, in the conventional piezoelectric pumps, the entire piezoelectric element is attached to a movable part of the diaphragm as shown in, for example, FIG. 1 in Japanese Patent Application Laid-Open No. H10-299659. Though the diaphragm operates according to the displacement of the piezoelectric element, the piezoelectric element itself, which is a driving means for that operation, is fixed only to the diaphragm. The inventors of the present invention found that, due to this construction, the displacement of the piezoelectric element and the motion of the diaphragm interfere with each other, thereby making it impossible to stably transfer a fluid as a pump. The inventors of the present invention then found that, by fixing a part of the piezoelectric element so as not to be displaced, the piezoelectric element is displaced with that part as a fulcrum, and the displacement of the piezoelectric element maintains stability even with the motion of the member which functions as the diaphragm. As a result of further conducting detailed study, the inventors of the present invention completed the present invention.

Which is to say, the present invention provides a piezoelectric pump including: a structure including a piezoelectric element and a support member that supports the piezoelectric element; and a first substrate and a second substrate that sandwich the structure, wherein the piezoelectric pump has: a pump chamber surrounded by the second substrate and the structure; and a first opening and a second opening that are communicated with the pump chamber, and wherein a space is provided so that the structure flexes in a direction opposite to the pump chamber according to an operation of the piezoelectric element.

Preferably, the piezoelectric pump according to the present invention has a void surrounded by the first substrate and the structure. In this piezoelectric pump according to the present invention, when a voltage is applied to the piezoelectric element, a piezoelectric body constituting the piezoelectric element is displaced in an in-plane direction (d31 direction) and a thickness direction (d33 direction). With this displacement, the structure vibrates in the thickness direction with a part fixed to the first substrate and/or the second substrate as a fulcrum, due to shape effects with the support member. This vibration changes a volume and an internal pressure of the pump chamber which serves as a flow path of a fluid, as a result of which the fluid is transferred in the piezoelectric pump through the first opening, the pump chamber, and the second opening.

In this piezoelectric pump according to the present invention, the piezoelectric element which is a source of vibration is sandwiched between the first and second substrates and therefore is in a state of not being directly exposed to outside. Besides, the pump chamber and the void are present around the piezoelectric element, so that the vibration of the piezoelectric element is absorbed by these pump chamber and void which are spaces sandwiched between the first and second substrates. Consequently, the piezoelectric pump according to the present invention can adequately suppress the propagation of the vibration by the piezoelectric element to outside, and also suppress signal noise associated with the vibration. Furthermore, the piezoelectric pump according to the present invention has a construction in which the piezoelectric element is not provided outside the first and second substrates but sandwiched between the first and second substrates. This allows elements and circuits other than the piezoelectric element constituting the piezoelectric pump to be provided outside the first and second substrates. Hence an electronic component including the piezoelectric pump according to the present invention can be integrated with higher density.

Preferably, in the piezoelectric pump according to the present invention, at least one of the piezoelectric element and the support member has a constriction in at least one of an in-plane direction and a thickness direction of the piezoelectric element. When a constriction is provided in the piezoelectric element and/or the support member, a load imposed on the constricted part per unit cross-sectional area according to the vibration of the structure becomes larger as compared with an unconstructed part. When this load per unit cross-sectional area is larger, a vibration amplitude of the structure is larger. This being so, when a predetermined voltage is applied to the piezoelectric element of the above-mentioned piezoelectric pump, the structure exhibits a larger vibration amplitude (operation amplitude) than a structure with no constriction. This contributes to a further increase in fluid transferring amount by the piezoelectric pump.

Moreover, the present invention provides a fluid transferring system including a first valve unit, a piezoelectric pump unit, and a second valve unit in the stated order along a flow direction of a fluid, wherein the piezoelectric pump unit includes: a first structure including a first piezoelectric element and a first support member that supports the first piezoelectric element; and a first substrate and a second substrate that sandwich the first structure, the piezoelectric pump unit has: a pump chamber surrounded by the second substrate and the first structure; and a first opening and a second opening that are communicated with the pump chamber, and a space is provided so that the first structure flexes in a direction opposite to the pump chamber according to an operation of the first piezoelectric element, wherein the first valve unit includes: a second structure including a second piezoelectric element and a second support member that supports the second piezoelectric element; and the first substrate and the second substrate that sandwich the second structure, and the first valve unit is opened or closed by a part of the second structure becoming out of or into contact with a part of the first substrate or the second substrate according to an operation of the second piezoelectric element, and wherein the second valve unit includes: a third structure including a third piezoelectric element and a third support member that supports the third piezoelectric element; and the first substrate and the second substrate that sandwich the third structure, and the second valve unit is opened or closed by a part of the third structure becoming out of or into contact with a part of the first substrate or the second substrate according to an operation of the third piezoelectric element.

The fluid transferring system according to the present invention includes the piezoelectric pump according to the present invention as the piezoelectric pump unit, and therefore can adequately suppress the propagation of the vibration to outside for the same reason as above. In addition, in the fluid transferring system according to the present invention, the first and second valve units each including the piezoelectric element are also sandwiched between the first and second substrates, and so are not directly exposed to outside. Accordingly, the vibration associated with the operations of these valve units can be suppressed, too. Furthermore, the fluid transferring system according to the present invention has a construction in which the piezoelectric elements included in the piezoelectric pump unit and the first and second valve units are not provided outside the first and second substrates but sandwiched between the first and second substrates. This allows elements and circuits other than the piezoelectric elements to be provided outside the first and second substrates. Hence an electronic component including the fluid transferring system according to the present invention can be integrated with higher density.

Preferably, in the piezoelectric pump according to the present invention, the structure includes two or more piezoelectric elements arranged in a flow direction of a fluid, and one support member that supports the two or more piezoelectric elements, and the piezoelectric pump has a void surrounded by the first substrate and the structure. In this piezoelectric pump according to the present invention, by applying a voltage sequentially to the piezoelectric elements from a piezoelectric element located on a fluid inlet side (upstream side) to a piezoelectric element located on a fluid outlet side (downstream side), the plurality of piezoelectric elements move in a peristaltic manner as a whole, thereby transferring the fluid. Since one pair of electrodes are provided on one piezoelectric element in the piezoelectric pump according to the present invention, the size of the piezoelectric element is not large with respect to the electrodes, and the range of bend of the electrodes with the displacement of the piezoelectric element is not large. Accordingly, the piezoelectric pump can adequately suppress electrode peeling. Moreover, the piezoelectric pump according to the present invention includes two or more piezoelectric elements supported by one support member, where a voltage applied to one piezoelectric element does not affect the displacement of the other piezoelectric element. Therefore, the piezoelectric pump can operate with sufficient stability in high speed driving, and also a variation in displacement amount of the piezoelectric elements can be adequately suppressed.

Moreover, the piezoelectric pump according to the present invention transfers the fluid, by displacing the upstream piezoelectric element to push out the fluid and also displacing the downstream piezoelectric element to suck in the fluid. By appropriately combining the pushing and sucking of the fluid in this way, the piezoelectric pump according to the present invention exhibits higher efficiency, and a larger fluid transferring amount can be realized with application of a small voltage. Further, since each pump chamber is surrounded by the second substrate and the structure in the piezoelectric pump according to the present invention, the displacement of the piezoelectric element in each pump chamber can be efficiently converted to compression (pressurization) and expansion (depressurization) of the fluid. Besides, the fluid is movable only from each pump chamber to its adjacent pump chamber, so that the above-mentioned compression and expansion can be efficiently converted to the fluid transfer between pump chambers. As a result, the piezoelectric pump according to the present invention can convert the voltage applied to the piezoelectric elements to the fluid transferring amount more efficiently.

Moreover, in the piezoelectric pump according to the present invention, the piezoelectric elements are sandwiched between the first and second substrates and so are in a state of being not directly exposed to outside, and the void is present around the piezoelectric elements. That is, in the piezoelectric pump according to the present invention, the piezoelectric elements which are a source of vibration are not directly exposed to outside, and the vibration is absorbed by the above-mentioned void. As a result, the piezoelectric pump according to the present invention can suppress the propagation of the vibration by the piezoelectric elements to outside, and also suppress signal noise associated with the vibration. Furthermore, the piezoelectric pump according to the present invention has a construction in which the piezoelectric elements are not provided outside the first and second substrates but sandwiched between the first and second substrates. This allows elements and circuits other than the piezoelectric elements constituting the piezoelectric pump to be provided outside the first and second substrates. Hence an electronic component including the piezoelectric pump according to the present invention can be integrated with higher density.

Preferably, in the piezoelectric pump according to the present invention, the support member is a thin film, a part of a main surface of the support member facing the pump chamber having a planar shape in which two or more circular surfaces are partially overlapped with each other, and each of the two or more piezoelectric elements is a thin film that is supported on the two or more circular surfaces and has a circular main surface. When a voltage is applied to each piezoelectric element, the thin-film piezoelectric element is displaced in the thickness direction (d33 direction) and also displaced radially in the in-plane direction (d31 direction). This causes the piezoelectric pump to operate by bending in the thickness direction. Accordingly, by making the main surfaces of the plurality of thin-film piezoelectric elements and the main surface of the support member for these piezoelectric elements facing the pump chamber closer to a circular shape, the applied voltage can be converted to the fluid transferring amount more efficiently, and also the piezoelectric pump can be improved in durability and life expectancy by suppressing warpage of the piezoelectric elements.

Preferably, in the piezoelectric pump according to the present invention, each of the two or more piezoelectric elements includes a piezoelectric body and one pair of electrodes sandwiching the piezoelectric body, and the piezoelectric pump has three or more wires led out alternately from the pair of electrodes along the flow direction of the fluid. When a voltage is applied, each piezoelectric element is displaced in the thickness direction and the in-plane direction, and accordingly bends. Here, the top of the bent piezoelectric element is a part that is slightly closer to a connection part between an electrode and a wire led out from the electrode, than a central part of the piezoelectric element in the in-plane direction. In the case where the connection parts between the electrodes sandwiching the piezoelectric element and the wires are different in the in-plane direction of the piezoelectric element, the top of the bent piezoelectric element is a part that is slightly closer to an imaginary connection part at an intermediate point between these connection parts than the central part of the piezoelectric element in the in-plane direction. When one pair of electrodes in the piezoelectric element has three or more connection parts alternately along the flow direction of the fluid, by applying a voltage sequentially to the lead-out parts from upstream to downstream, the top of the bent piezoelectric element sequentially moves from upstream to downstream. In this way, the applied voltage can be converted to the fluid transferring amount more efficiently.

Preferably, in the piezoelectric pump according to the present invention, the piezoelectric element includes a displacement part that is displaced by application of a voltage, and a fixed part that is fixed by being directly or indirectly sandwiched between the first substrate and the second substrate, and from a state where the first substrate is joined to the structure, a part of the first substrate facing the displacement part and a surrounding part of the support member surrounding a periphery of the displacement part is removed so as to expose the displacement part and the surrounding part. In the piezoelectric pump according to the present invention having this construction, when a voltage is applied to the piezoelectric element, the piezoelectric body constituting the piezoelectric element is displaced in the in-plane direction (d31 direction) and the thickness direction (d33 direction). With this displacement, the structure vibrates in the thickness direction with a part fixed to the first substrate and/or the second substrate as a fulcrum, due to shape effects with the support member. This vibration changes a volume and an internal pressure of the pump chamber which serves as a fluid flow path, as a result of which the fluid is transferred in the piezoelectric pump through the first opening, the pump chamber, and the second opening.

Moreover, in the piezoelectric pump according to the present invention, since the fixed part is fixed by being directly or indirectly sandwiched between the first and second substrates, the displacement of the fixed part is suppressed (regulated) even when a voltage is applied to the piezoelectric element. Therefore, the piezoelectric element vibrates by the displacement part being displaced with the fixed part as a fulcrum. Consequently, the conventional problem described above, namely, the interference between the displacement of the piezoelectric element and the motion of the support member which functions as a diaphragm, can be adequately suppressed. Thus, the piezoelectric pump according to the present invention enables the fluid to be transferred stably.

Furthermore, in the piezoelectric pump according to the present invention, from a state where the first substrate is joined to the above-mentioned structure, a part of the first substrate facing the displacement part and a surrounding part of the support member surrounding a periphery of the displacement part is removed by etching, so as to expose the displacement part and the surrounding part. This allows the displacement part and the surrounding part to release, to outside, tensile stress and compressive stress (hereafter simply referred to as “stress”) which occur due to the restraint of being joined to the first substrate. Meanwhile, the other parts of the first substrate remain (continuously) joined to and supported by the structure. Thus, the structure can be accurately and reliably fixed to the first substrate, so that the fluid can be transferred more stably.

Here, the motion of the above-mentioned structure in the piezoelectric pump is more stable when both sides are fixed by sandwiching rather than when only one side (for example, the second substrate side in the present invention) is fixed, because the part that functions as the fulcrum of the motion is supported more firmly. In the case of the construction such as the piezoelectric pump according to the present invention, there are the following methods to fix the structure by the first substrate: a method of joining the first substrate to a part of the structure other than an motion part, from a state where nothing is joined to the surface of the structure opposite to the second substrate; and a method of joining the first substrate to the entire surface of the structure opposite to the second substrate and then selectively removing only a part of the first substrate joined to the motion part.

According to the former method, the first substrate is partially joined to one side of the structure. At this time, the motion part that is not joined to the first substrate is partially relaxed or stretched. As a result, the stress (distribution) in the motion part becomes not uniform, and accordingly a variation in motion arises. Stable fluid transfer is difficult in a piezoelectric pump having such a construction. In a piezoelectric pump having the latter construction according to the present invention, on the other hand, the first substrate is joined to the entire surface of one side of the structure, so that the entire surface of the structure is restrained by the first substrate, and its stress (distribution) is uniform. Subsequently, even when the part of the first substrate joined to the displacement part and the surrounding part which constitute the motion part is removed to expose the motion part, the other parts remain restrained by the joint with the first substrate, and therefore the stress in the motion part is maintained uniform. The piezoelectric pump according to the present invention having such a construction can transfer the fluid with sufficient stability.

Furthermore, in the piezoelectric pump according to the present invention, not only the displacement part of the piezoelectric element but also the surrounding part of the support member surrounding the displacement part is exposed. Such a motion part is capable of a large motion (in other words, capable of being displaced to a large extent), which contributes to an increase in pump volume.

Preferably, in the piezoelectric pump according to the present invention, the piezoelectric element includes a first electrode, a piezoelectric body, and a second electrode that are laminated in the stated order in a direction from the first substrate to the second substrate, and a first laminate composed of the first electrode and the piezoelectric body has a smaller product of Young's modulus and thickness than the second electrode. Preferably, in the piezoelectric pump according to the present invention, the piezoelectric element further includes a hard layer on a surface of the second electrode facing the second substrate, and the first laminate has a smaller product of Young's modulus and thickness than a second laminate composed of the second electrode and the hard layer. According to this construction, the motion part of the structure tends to flex more toward the first substrate, while the extent of flex toward the second substrate decreases. This reduces an occurrence of a trouble in the operation of the piezoelectric element, so that the fluid can be transferred more stably.

Preferably, in the piezoelectric pump according to the present invention, the hard layer is made of at least one metal selected from the group consisting of chromium, tungsten, tantalum, and platinum. These metals are especially high in Young's modulus. Therefore, the fluid can be transferred more stably even when the hard layer is made thin, for the same reason as stated above. Hence this is advantageous for a more compact, thinner piezoelectric pump.

According to the present invention, it is possible to provide a piezoelectric pump and a fluid transferring system that adequately suppress propagation of a vibration by a piezoelectric element to outside. Moreover, according to the present invention, it is possible to provide a piezoelectric pump that adequately prevents electrodes included in a piezoelectric element from peeling, performs a sufficiently stable operation even in high speed driving, and adequately suppresses a variation in displacement amount. Furthermore, according to the present invention, it is possible to provide a piezoelectric pump that can transfer a fluid with sufficient stability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process chart schematically showing a manufacturing method of a piezoelectric pump according to a first embodiment of the present invention.

FIG. 2 is a process chart schematically showing the manufacturing method of the piezoelectric pump according to the first embodiment of the present invention.

FIG. 3 is a partially perspective top view schematically showing a fluid transferring system according to the first embodiment of the present invention.

FIG. 4 is a sectional view schematically showing the fluid transferring system according to the first embodiment of the present invention.

FIG. 5 is a schematic view showing various planar shapes of a piezoelectric element and a support member according to the first embodiment of the present invention.

FIG. 6 is a perspective top view schematically showing a piezoelectric pump according to a second embodiment of the present invention.

FIG. 7 is a schematic view showing an operation of the piezoelectric pump according to the second embodiment of the present invention.

FIG. 8 is a partially enlarged schematic sectional view showing the piezoelectric pump according to the second embodiment of the present invention.

FIG. 9 is a process chart schematically showing a manufacturing method of a piezoelectric pump according to a third embodiment of the present invention.

FIG. 10 is a top view schematically showing planar shapes of piezoelectric elements according to the third embodiment of the present invention.

FIG. 11 is a process chart schematically showing an operation of the piezoelectric pump according to the third embodiment of the present invention.

FIG. 12 is a top view schematically showing a piezoelectric pump according to a fourth embodiment of the present invention.

FIG. 13 is a process chart schematically showing an operation of the piezoelectric pump according to the fourth embodiment of the present invention.

FIG. 14 is a partially enlarged schematic sectional view showing the piezoelectric pump according to the fourth embodiment of the present invention.

FIG. 15 is a schematic view showing a sample in an example.

FIG. 16 is a plot chart showing an extent of flex of a structure when a thickness of a hard layer is changed.

FIG. 17 is a top view schematically showing a piezoelectric pump according to another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following describes a best mode (hereafter simply referred to as “embodiment”) for carrying out the present invention in detail, with reference to drawings according to need. Note that the same components in the drawings are given the same reference signs, and repeated description is omitted. Moreover, the positional relation of up, down, left, and right is based on the positional relation illustrated in the drawings, unless otherwise specified. Furthermore, scale ratios of the drawings are not limited to the illustrated scale ratios.

FIGS. 1 and 2 are process charts schematically showing a manufacturing method of a piezoelectric pump in a first embodiment of the present invention. First, in a step (A1), a lower electrode layer 104, a piezoelectric body layer 106, and an upper electrode layer 108 are laminated on a film formation substrate 102 in this order. In more detail, first the lower electrode layer 104 is formed on a surface of the film formation substrate 102 by, for example, sputtering, CVD, or vapor deposition. The film formation substrate 102 is not specifically limited so long as the lower electrode layer 104 and the piezoelectric body layer 106 can be formed on its surface, and may be a substrate used for normal thin film formation. In view of the combination with a material and a film formation method of the piezoelectric body layer 106 described later and in view of obtaining a highly-oriented piezoelectric body, however, the film formation substrate 102 is preferably a Si substrate. A material of the lower electrode layer 104 is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The lower electrode layer 104 may have a thickness of 0.05 μm to 1.0 μm, as an example.

Next, the piezoelectric body layer 106 is formed on a surface of the lower electrode layer 104, and on an exposed surface of the film formation substrate 102 according to need. A formation method of the piezoelectric body layer 106 may be sputtering, CVD, vapor deposition, or the like, but a film formation method using epitaxial growth on a Si substrate is particularly preferable because a piezoelectric body with high orientation and excellent piezoelectric properties can be obtained and also a manufacturing yield of a piezoelectric pump 170 can be improved. For instance, such a film formation method is disclosed in Japanese Patent Application Laid-Open No. 2000-332569 by the applicant of this application. A material of the piezoelectric body layer 106 is not specifically limited so long as it is a piezoelectric material capable of thin film formation. For example, PZT, barium titanate, and the like are applicable. PZT (lead zirconate titanate) is particularly preferable as it has excellent piezoelectric properties and also is easily available. In the case of using PZT as the material of the piezoelectric body layer 106 and forming the piezoelectric body layer 106 on the Si substrate by the film formation method using epitaxial growth, it is preferable to form a PZT (001) thin film on Si (100) by epitaxial growth, in view of obtaining especially excellent orientation. The piezoelectric body layer 106 may have a thickness of 0.5 μm to 5.0 μm, as an example.

Following this, the upper electrode layer 108 is formed on a surface of the piezoelectric body layer 106 by, for example, sputtering, CVD, or vapor deposition. A material of the upper electrode layer 108 is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The upper electrode layer 108 may have a thickness of 0.05 μm to 1.0 μm, as an example.

Next, in a step (A2), the lower electrode layer 104, the piezoelectric body layer 106, and the upper electrode layer 108 laminated as described above are patterned to a desired shape. A method of the patterning is not specifically limited. As an example, after forming a mask resist on a surface of the upper electrode layer 108 as an etch mask, a part of each of the above-mentioned layers not covered by the mask resist is removed by etching, and then the mask resist is removed. As an alternative patterning method, a liftoff method of performing resist patterning, film formation, and unwanted part removal may be used. As a result, a piezoelectric element 120 including a lower electrode 114, a piezoelectric body 116, and an upper electrode 118 which are laminated in this order is obtained. Here, in addition to or instead of this step (A2), the lower electrode layer 104, the piezoelectric body layer 106, and the upper electrode layer 108 may be directly patterned with film formation by, for example, laser writing. The piezoelectric element 120 may be obtained by repeatedly performing film formation and patterning for each layer.

Next, in a step (A3), a first insulating member 122 is formed on surfaces of the film formation substrate 102 and the piezoelectric element 120. The first insulating member 122 is a member that constitutes a part of a support member of the piezoelectric pump. A material of the first insulating member 122 is an insulating material, and preferably a flexible material since the first insulating member 122 needs to bend according to the displacement of the piezoelectric body 116 without being damaged. When a flexible material is employed as the material of the first insulating member 122, the displacement of the piezoelectric body 116 can be favorably transmitted to a pump chamber, which enhances the efficiency of the piezoelectric pump. In detail, the material of the first insulating member 122 is preferably a resin material. In the case where the material of the first insulating member 122 is a resin material, the step (A3) is performed as follows. First, a resin composition (for example, a mixture of a solvent and a resin and/or a monomer) which is a raw material of the resin material is applied onto the surfaces of the film formation substrate 102 and piezoelectric element 120. After the applied resin composition is solidified by drying or the like or hardened by heating, optical irradiation, or the like, the resin composition is patterned to a desired shape. The patterning may be performed using a known method of patterning a resin material. For example, a photolithography method is applicable. As the resin material, a material that favorably adheres to the film formation substrate 102 and the piezoelectric element 120 and also has favorable patterning properties such as developability is preferable. For example, a silicone resin, polyimide, parylene, and the like are applicable. A surface shape of the first insulating member 122 obtained by patterning may be any shape suitable as a wall surface forming the pump chamber of the piezoelectric pump. Thus, a first complex 126 including the film formation substrate 102 and the piezoelectric element 120 and the first insulating member 122 which are formed on the film formation substrate 102 is obtained.

Meanwhile, in a step (B1), first a substrate 130 is prepared. For example, the substrate 130 is a glass substrate or a ceramic substrate, and has a thickness of 0.2 mm to 2.0 mm. Following this, in a step (B2), a surface of the substrate 130 is processed to a predetermined shape by etching or the like. Further, in a step (B3), a first opening 130 a and a second opening 130 b are formed through the substrate 130 in its thickness direction by etching or the like, at predetermined positions. Thus, a second substrate 132 having the openings 130 a and 130 b is obtained. Here, a surface shape of the second substrate 132 obtained by processing may be any shape suitable as a wall surface forming the pump chamber of the piezoelectric pump.

Next, in a step (C1), the second substrate 132 is attached to the first complex 126 on a side where the first insulating member 122 is formed. When doing so, positioning is performed so that the surface of the second substrate 132 processed by etching or the like faces the first complex 126 and also the openings 130 a and 130 b are communicated with the pump chamber of the piezoelectric pump.

A method of the attachment may be a method of applying, for example, an adhesive or a resin to an area of contact between the first complex 126 and the second substrate 132. Next, in a step (C2), the film formation substrate 102 is removed by etching or the like. In this way, a second complex 140 including the piezoelectric element 120, the first insulating member 122, and the second substrate 132 is obtained.

Meanwhile, in a step (D1), a third complex 146 including a first substrate 142 and a sensor 144 disposed on a surface of the first substrate 142 is prepared. For example, the first substrate 142 is a glass substrate or a ceramic substrate, and has a thickness of 0.2 mm to 2.0 mm. The sensor 144 is a sensor for detecting a flow amount and a temperature of a fluid flowing in the piezoelectric pump, and may be a known thermopile sensor as an example.

Next, in a step (D2), a second insulating member 148 is formed on a surface of the first substrate 142 where the sensor 144 is disposed. The second insulating member 148 is a member constituting a part of the support member of the piezoelectric pump, as with the first insulating member 122. Accordingly, a material of the second insulating member 148 is an insulating material, and preferably a flexible material because the second insulating member 148 needs to be undamaged by the displacement of the piezoelectric element 120. In detail, the material of the second insulating member 148 is preferably a resin material. In addition, in order to attain a favorable joint with the first insulating member 122, the material of the second insulating member 148 is preferably the same material (for example, having the same resin composition as a raw material) as the first insulating member 122. In the case where the material of the second insulating member 148 is a resin material, the step (D2) is performed as follows. First, a resin composition (for example, a mixture of a solvent and a resin and/or a monomer) which is a raw material of the resin material is applied onto the surface of the first substrate 142, and onto a surface of the sensor 144 according to need. After the applied resin composition is solidified by drying or the like or hardened by heating, optical irradiation, or the like, the resin composition is patterned to a desired shape. The patterning may be performed using a known method of patterning a resin material. For example, a photolithography method is applicable. As the resin material, a material that favorably adheres to the first substrate 142 and the sensor 144 and also has favorable patterning properties such as developability is preferable. For example, a silicone resin, polyimide, parylene, and the like are applicable. A shape of the second insulating member 148 obtained by patterning may be any shape suitable for forming a void of the piezoelectric pump together with the first substrate 142, the first insulating member 122, and the piezoelectric element 120. Thus, a fourth complex 150 including the third complex 146 and the second insulating member 148 is obtained.

Next, in a step (E), the second complex 140 and the fourth complex 150 are joined together at the first insulating member 122 and the second insulating member 148, as a result of which the piezoelectric pump 170 of this embodiment is obtained. When doing so, positioning is performed so that the first substrate 142, the first insulating member 122, the second insulating member 148, and the piezoelectric element 120 form the void of the piezoelectric pump 170. A method of joining the first insulating member 122 and the second insulating member 148 is not specifically limited. For example, an adhesive may be applied to an area of contact between the first insulating member 122 and the second insulating member 148. Alternatively, in the case where the materials of the first insulating member 122 and the second insulating member 148 are capable of thermo-compression bonding, the first insulating member 122 and the second insulating member 148 may be brought into contact with each other and then heated.

The obtained piezoelectric pump 170 of this embodiment includes: a structure 174 including the piezoelectric element 120 and a support member 172 that supports the piezoelectric element 120; and the first substrate 142 and the second substrate 132 that sandwich the structure 174, and has: a void 176 surrounded by the first substrate 142 and the structure 174; a pump chamber 178 surrounded by the second substrate 132 and the structure 174; and the first opening 130 a and the second openings 130 b that are communicated with the pump chamber 178.

In more detail, the structure 174 included in the piezoelectric pump 170 of this embodiment includes the piezoelectric element 120 and the support member 172 which is directly joined to the piezoelectric element 120 to support the piezoelectric element 120. The support member 172 has a central part 172 a in film form, and a peripheral part 172 b that surrounds the central part 172 a and is thicker than the central part 172 a. The piezoelectric element 120 is in thin film form, and is disposed so as to be embedded at a lower side of the central part 172 a of the support member 172. The support member 172 and the piezoelectric element 120 are joined so that the support member 172 covers a surface of the piezoelectric element 120 closer to the pump chamber (flow path) 178. The central part 172 a of the support member 172 and the piezoelectric element 120 are located at about a center in a thickness direction of the peripheral part 172 b of the support member 172, and spaces (the pump chamber 178 and the void 176) are secured on both sides of the central part 172 a of the support member 172 and the piezoelectric element 120 in their thickness direction.

An upper surface of the first substrate 142 is joined to a lower surface of the peripheral part 172 b of the support member 172. This forms the void 176 surrounded by the first substrate 142, the support member 172, and the piezoelectric element 120. In addition, the sensor 144 is fixed by being sandwiched between the upper surface of the first substrate 142 and the lower surface of the peripheral part 172 b of the support member 172.

A middle portion of the central part 172 a of the support member 172 protrudes upward, due to the embedment of the piezoelectric element 120. Moreover, a lower surface of the second substrate 132 is joined to an upper surface of the peripheral part 172 b of the support member 172. This forms the pump chamber 178 surrounded by the second substrate 132 and the support member 172. A lower surface of a central part 132 a of the second substrate 132 is situated higher than a lower surface of a peripheral part 132 b of the second substrate 132, in order to prevent a decrease in volume of the pump chamber 178 due to the protrusion of the central part 172 a of the support member 172. In addition, the second substrate 132 has the first opening 130 a and the second opening 130 b passing through in its thickness direction. These openings 130 a and 130 b are communicated with the pump chamber 178.

In the piezoelectric pump 170 of this embodiment, when a voltage is applied to the piezoelectric element 120 through the lower electrode 114 and the upper electrode 118 which are driving electrodes, the thin-film piezoelectric body 116 is displaced in the in-plane direction (d31 direction) and the thickness direction (d33 direction). In particular, since the piezoelectric element 120 is in thin film form and also its peripheral part is fixed by the support member 172, the piezoelectric element 120 bends in the thickness direction according to the displacement of the piezoelectric body 116 in the in-plane direction. By switching the voltage application between ON and OFF or switching a direction of the applied voltage between forward and backward (applying an alternating-current voltage), the structure 174 vibrates in the thickness direction, with the peripheral part 172 b of the support member 172 fixed by the first substrate 142 and the second substrate 132 as a fulcrum. This vibration changes the volume and internal pressure of the pump chamber 178 which also functions as the flow path, as a result of which the fluid is transferred in the piezoelectric pump through the first opening 130 a, the pump chamber 178, and the second opening 130 b. In this embodiment, the vibration of the structure 174 is absorbed by the void 176 and the pump chamber 178, so that the propagation of the vibration to outside the first substrate 142 and the second substrate 132 is adequately suppressed. With this vibration suppression, signal noise caused by the vibration is also suppressed. Furthermore, while the structure 174 is firmly fixed by being sandwiched between the first substrate 142 and the second substrate 132, the void 176 permits the movement of the structure 174 in the thickness direction and particularly the flex of the structure 174 toward the first substrate 142. Hence the piezoelectric pump 170 of this embodiment can realize a large flow amount by application of a small voltage.

Moreover, in the piezoelectric pump 170 of this embodiment, in the case where a Pb (lead) containing material such as PZT is adopted as the material of the piezoelectric body 116, Pb generated from the piezoelectric body 116 can be prevented from scattering to outside the piezoelectric pump 170, because the piezoelectric body 116 is surrounded by the first substrate 142 and the support member 172.

Furthermore, the piezoelectric pump 170 of this embodiment employs the thin-film piezoelectric element 120 which is displaced by a low voltage, so that favorable efficiency can be exhibited even with a lower voltage. In addition, by making the piezoelectric element 120 in thin film form, a piezoelectric pump of an optimum shape in accordance with design can be manufactured when compared with the so-called bulk-type piezoelectric pump. Moreover, by employing the thin-film piezoelectric element 120, the piezoelectric pump can be made more compact and thinner when compared with the bulk-type piezoelectric pump. This enables an electronic component including the piezoelectric pump 170 to be integrated with higher density, thereby lending itself to effective use for MEMS.

Since a thin-film piezoelectric element has a small pump volume, a vibration frequency needs to be increased by applying a high-frequency voltage, in order to increase a fluid flow amount. However, there is a problem that the vibration of the piezoelectric element is more likely to propagate to outside when the vibration frequency is increased. In the piezoelectric pump 170 of this embodiment, on the other hand, the propagation of the vibration to outside is adequately suppressed as mentioned above, and therefore this problem can be avoided even when the piezoelectric element 120 is driven at high frequencies.

Further, the piezoelectric pump 170 has a construction in which the piezoelectric element 120 is not provided outside the first substrate 142 and the second substrate 132 but sandwiched between the first substrate 142 and the second substrate 132. This construction, combined with the suppression of the vibration to outside the piezoelectric pump 170, allows circuits and elements other than the piezoelectric element 120 to be provided outside the first substrate 142 and the second substrate 132, even when such circuits and elements have a poor vibration resistance. In this respect too, the piezoelectric pump 170 can realize higher density integration, and lends itself to effective use for MEMS. In addition, by disposing the piezoelectric element 120 so as to be embedded at the lower side of the central part 172 a of the support member 172, the joint between the piezoelectric element 120 and the support member 172 is enhanced. This contributes to improved durability of the piezoelectric pump 170.

FIGS. 3 and 4 are schematic views showing a fluid transferring system of this embodiment. FIG. 3 is a partial perspective top view, and FIG. 4 is a sectional view showing a section taken along the line I-I in FIG. 3. A fluid transferring system 300 of this embodiment is a fluid transferring system that includes a first valve unit 302, a piezoelectric pump unit 304, and a second valve unit 306 in this order along a fluid flow direction (direction shown by the arrow in FIG. 4). The piezoelectric pump unit 304 includes: a first structure 312 including a first piezoelectric element 308 and a first support member 310 that supports the first piezoelectric element 308; and a first substrate 314 and a second substrate 316 that sandwich the first structure 312, and has: a void 318 surrounded by the first substrate 314 and the first structure 312; a pump chamber 320 surrounded by the second substrate 316 and the first structure 312; and a first opening 322 and a second opening 324 that are communicated with the pump chamber 320.

In more detail, the first structure 312 included in the piezoelectric pump unit 304 includes the first piezoelectric element 308 and the first support member 310 directly joined to the first piezoelectric element 308. The first piezoelectric element 308 has a construction in which a piezoelectric body is sandwiched between two upper and lower electrodes, and can be realized with the same construction and material as the piezoelectric element 120 described earlier. The first support member 310 has a central part 310 a in film form, and a peripheral part 310 b which surrounds the central part 310 a and is thicker than the central part 310 a. The first piezoelectric element 308 is in thin film form, and is disposed so as to be embedded at a lower side of the central part 310 a of the first support member 310. The central part 310 a of the first support member 310 and the first piezoelectric element 308 are located at about a center in a thickness direction of the peripheral part 310 b of the first support member 310 (an upper part of the first support member 310 is not shown in FIG. 4 because of the presence of the openings 322 and 324 described later), and spaces (the pump chamber 320 and the void 318) are secured on both sides of the central part 310 a of the first support member 310 and the first piezoelectric element 308 in their thickness direction.

In the piezoelectric pump unit 304, an upper surface of the first substrate 314 is joined to a lower surface of the peripheral part 310 b of the first support member 310. This forms the void 318 surrounded by the first substrate 314 and the first structure 312.

A middle portion of the central part 310 a of the first support member 310 protrudes upward, due to the embedment of the first piezoelectric element 308. Moreover, a lower surface of the second substrate 316 is joined to an upper surface of the peripheral part 310 b of the first support member 310. This forms the pump chamber 320 surrounded by the second substrate 316 and the first structure 312, for transferring the fluid. The piezoelectric pump unit 304 further has the first opening 322 formed by the first support member 310 and the second substrate 316 at a point where the pump chamber 320 and the first valve unit 302 are communicated with each other, and the second opening 324 formed by the first support member 310 and the second substrate 316 at a point where the pump chamber 320 and the second valve unit 306 are communicated with each other. In addition, a wire 346 led out from the upper and lower electrodes extends from the first piezoelectric element 308 to a terminal 348, and is connected to a power supply (not illustrated) via the terminal 348.

This piezoelectric pump unit 304 operates in the same way as the above-mentioned piezoelectric pump 170. Since the operation of the piezoelectric pump unit 304 can be easily understood by a person skilled in the art from the above description of the piezoelectric pump 170 and with reference to FIGS. 2, 3, and 4, its detailed description is omitted here.

As is clear from FIG. 3, in the piezoelectric pump unit 304 of this embodiment, the first piezoelectric element 308 has a constriction 340 in its in-plane direction. This improves the displacement by the same voltage, so that a voltage applied to obtain a desired fluid transferring amount can be reduced when compared with a piezoelectric element with no constriction. In other words, when a predetermined voltage is applied, the first piezoelectric element 308 has a larger vibration amplitude than a piezoelectric element with no constriction. This contributes to a further increase in fluid transferring amount by the piezoelectric pump unit 304. Moreover, as is clear from FIG. 4, in the piezoelectric pump unit 304 of this embodiment, the first support member 310 is also joined to a lower surface of one edge (the right edge in FIG. 4) of the first piezoelectric element 308, and supports this edge of the first piezoelectric element 308 in a sandwiching manner. Thus, the edge of the first piezoelectric element 308 can be fixed more firmly, which contributes to enhanced mechanical strength.

The first valve unit 302 includes: a second structure 330 including a second piezoelectric element 326 and a second support member 328 that supports the second piezoelectric element 326; and the first substrate 314 and the second substrate 316 that sandwich the second structure 330, and is opened or closed by a part of the second structure 330 becoming out of or into contact with a part of the second substrate 316 according to an operation of the second piezoelectric element 326.

In more detail, the second structure 330 included in the first valve unit 302 includes four second piezoelectric elements 326 and the second support member 328 that is directly joined to the second piezoelectric elements 326 to support the second piezoelectric elements 326. The second piezoelectric elements 326 each have a construction in which a thin-film piezoelectric body is sandwiched between two upper and lower electrodes, and can be realized with the same material as the above-mentioned piezoelectric element 120. In the fluid transferring system 300 of this embodiment, the four second piezoelectric elements 326 have a planar shape which is a convergent hexagon having a tapered part, and are disposed with the tapered part directed to a hole 329 a in the second support member 328 described later so as to surround the hole 329 a, as shown in FIG. 3. Moreover, a wire 342 led out from the upper and lower electrodes extends from each of the second piezoelectric elements 326 to a terminal 344, and is connected to a power supply (not illustrated) via the terminal 344.

The second support member 328 includes a thin film part 329 that is joined to the second piezoelectric elements 326 from above, a first joint 331 that joins a part of the second piezoelectric elements 326 opposite to the tapered part to the first substrate 314, and a second joint 332 that joins a part of the second piezoelectric elements 326 opposite to the tapered part to the second substrate 316. The thin film part 329 is shaped like a circular ring. The thin film part 329 is joined onto the second piezoelectric elements 326, and has the hole 329 a passing through in the thickness direction at its center. The second support member 328 can be realized with the same material as the above-mentioned support member 172.

A protrusion 314 a that protrudes downward from the second substrate 316 and whose lower surface has a flat disk shape, is provided on the thin film part 329 in the second support member 328 with a space therebetween. This protrusion 314 a is positioned so that its central part is directly above the hole 329 a in the thin film part 329 of the second support member 328 and also the protrusion 314 a at least partially overlaps with the four second piezoelectric elements 326 in its thickness direction. A diameter of the disk of the protrusion 314 a is slightly smaller than that of the thin film part 329.

When no voltage is applied to the second piezoelectric elements 326, the first valve unit 302 of this embodiment is in an open state in which a space is present between the protrusion 314 a of the second substrate and the second support member 328 and the fluid can flow in the space. When a voltage is applied to this first valve unit 302, the piezoelectric body in the second piezoelectric elements 326 is displaced in the in-plane direction (d31 direction) and the thickness direction (d33 direction), and bends downward in the thickness direction. Since the parts of the four second piezoelectric elements 326 opposite to the tapered parts are fixed to the first substrate 314 and the second substrate 316 respectively by the first joint 331 and the second joint 332, the tapered parts warp upward with the above-mentioned bend. As a result, the middle portion of the thin film part 329 of the second support member 328 is lifted up by the tapered parts, and an upper surface of the middle portion of the thin film part 329 is pressed against the lower surface of the protrusion 314 a of the second substrate. At this time, by adjusting each of the voltages applied to the four second piezoelectric elements 326, it is possible to control a pressure of pressing the thin film part 329 against the protrusion 314 a. Thus, the hole 329 a of the thin film part 329 is completely blocked by the protrusion 314 a of the second substrate. This causes the first valve unit 302 to be in a closed state, as a result of which the flow of the fluid can be blocked.

The second valve unit 306 includes: a third structure 336 including a third piezoelectric element 333 and a third support member 334 that supports the third piezoelectric element 333; and the first substrate 314 and the second substrate 316 that sandwich the third structure 336, and is opened or closed by a part of the third structure 336 becoming out of or into contact with a part of the second substrate 316 according to an operation of the third piezoelectric element 333. This second valve unit 306 has the same construction and operation as the first valve unit 302, where the third piezoelectric element 333, the third support member 334, and the third structure 336 respectively correspond to the second piezoelectric element 326, the second support member 328, and the second structure 330 in the first valve unit 302. Since the construction and operation of the second valve unit 306 can be understood by a person skilled in the art from the above description of the first valve unit 302 and with reference to FIGS. 3 and 4, its detailed description is omitted here.

The fluid transferring system 300 of this embodiment has an inlet port 350 on an upstream side of the first valve unit 302 and an outlet port 352 on a downstream side of the second valve unit 306, in addition to the first valve unit 302, the piezoelectric pump unit 304, and the second valve unit 306 described above. The inlet port 350 and the outlet port 352 are each a through hole passing through the second substrate 316 in the thickness direction.

A fluid transferring method using the fluid transferring system 300 of this embodiment is, for example, a method that repeats the following first step, second step, third step, and fourth step in sequence. First, a voltage is applied only to the second valve unit 306, without applying a voltage to the first valve unit 302 and the piezoelectric pump unit 304 (first step). At this time, the first valve unit 302 is in an open state, the piezoelectric pump unit 304 is in a stopped state, and the second valve unit 306 is in a closed state, so that the fluid flows through the inlet port 350 and is filled up to immediately before the second valve unit 306. Next, a voltage is applied to the first valve unit 302 to put the first valve unit 302 in a closed state as mentioned earlier (second step). As a result, the downstream side of the first valve unit 302 is blocked from the inlet port 350, and the fluid becomes enclosed between the first valve unit 302 and the second valve unit 306. After this, a voltage is applied to the piezoelectric pump unit 304, to increase the pressure of the enclosed fluid (third step). The voltage application to the second valve unit 306 is then stopped to put the second valve unit 306 in an open state (fourth step). This causes the fluid increased in pressure to be discharged downstream of the second valve unit 306, and to flow out of the fluid transferring system 300 via the outlet port 352. Following this, the first step is performed again, where the voltage application to the first valve unit 302 and the piezoelectric pump unit 304 is stopped and a voltage is applied only to the second valve unit 306 to fill the fluid up to immediately before the second valve unit 306.

Note that the fluid transferring system 300 of this embodiment includes a sensor (for example, a thermopile sensor) 354 in the flow path, thereby making it possible to detect a temperature, pressure, flow amount, and the like of the fluid flowing in the flow path. By feeding the temperature, pressure, and flow amount of the fluid detected by the sensor 354 back to the operation of the fluid transferring system and controlling operation conditions of the piezoelectric pump unit 304 in particular, it is possible to adjust the temperature and the like.

The fluid transferring system 300 of this embodiment includes the piezoelectric pump unit 304 described above, and therefore can achieve the same effects as the above-mentioned effects by the piezoelectric pump 170. Moreover, the fluid transferring system 300 of this embodiment has a construction in which not only the piezoelectric pump unit 304 but also the first valve unit 302 and the second valve unit 306 are sandwiched between the first substrate 314 and the second substrate 316. Accordingly, the fluid transferring system 300 can also suppress the vibration associated with the operations of these valve units 302 and 306. In addition, in the case where a Pb (lead) containing material such as PZT is employed as the material of the piezoelectric body included in any of the piezoelectric pump unit 304, the first valve unit 302, and the second valve unit 306, Pb generated from the piezoelectric body can be prevented from scattering to outside the fluid transferring system 300 more adequately, because the piezoelectric body is surrounded by the first substrate 314 and the second substrate 316. Furthermore, various elements and circuits can be provided outside the first substrate 314 and the second substrate 316 in the fluid transferring system 300. Thus, the fluid transferring system 300 can realize higher density integration, thereby lending itself to effective use for a product that applies MEMS technology.

Moreover, the fluid transferring system 300 of this embodiment employs the thin-film piezoelectric elements, so that favorable operation efficiency can be exhibited even with a lower voltage. In addition, by making the piezoelectric elements in thin film form, a fluid transferring system of an optimum shape in accordance with design can be manufactured when compared with the case of using the so-called bulk-type piezoelectric elements. Further, by employing the thin-film piezoelectric elements, the fluid transferring system can be made more compact and thinner when compared with the case of using the bulk-type piezoelectric elements. This enables an electronic component including the fluid transferring system 300 to be integrated with higher density, thereby lending itself to effective use for MEMS.

FIG. 6 is a perspective top view schematically showing a piezoelectric pump of a second embodiment of the present invention. FIG. 7 is a schematic view showing an operation of the piezoelectric pump of this embodiment, where (A) schematically shows a cross section taken along the line II-II in FIG. 6. FIG. 8 is a partially enlarged schematic sectional view showing the piezoelectric pump of this embodiment. A piezoelectric pump 200 of this embodiment includes: a structure 220 including six piezoelectric elements 202, 204, 206, 208, 210, and 212 (collectively written as “202 to 212”, the same applies hereafter) arranged along a flow direction of a fluid (the direction of the arrow A in FIG. 6) and one support member 214 that supports these piezoelectric elements 202 to 212; and a first substrate 222 and a second substrate 224 that sandwich the structure 220, and has: a void 226 surrounded by the first substrate 222 and the structure 220; a pump chamber 230 surrounded by the second substrate 224 and the structure 220; and a first opening 250 and a second opening 252 that are communicated with the pump chamber 230.

In more detail, the structure 220 included in the piezoelectric pump 200 of this embodiment includes the six piezoelectric elements 202 to 212 mentioned above, and the single support member 214 that is directly joined to these piezoelectric elements 202 to 212 to support the piezoelectric elements 202 to 212. The support member 214 is a thin film that is made of a material such as a resin and has a thickness of 1.0 μm to 10 μm, as an example. A part 214 a of one main surface (upper surface) of the support member 214 facing the pump chamber 230 has a planar shape like a cross-section of a string of beads where six circular surfaces put in a row are partially overlapped with each other at their peripheries.

The piezoelectric elements 202 to 212 are in thin film form with a thickness of 0.5 μm to 10.0 μm as an example, and have circular main surfaces. As shown in FIG. 8, the piezoelectric elements 202 to 212 respectively include lower electrodes 202 a to 212 a (the lower electrodes 210 a and 212 a included respectively in the piezoelectric elements 210 and 212 are not illustrated), piezoelectric bodies 202 b to 212 b (the piezoelectric bodies 210 b and 212 b included respectively in the piezoelectric elements 210 and 212 are not illustrated), and upper electrodes 202 c to 212 c (the upper electrodes 210 c and 212 c included respectively in the piezoelectric elements 210 and 212 are not illustrated), which are laminated in this order. The piezoelectric elements 202 to 212 are embedded in the support member 214 in a state where the respective lower electrodes 202 a to 212 a are exposed to the void 226. The piezoelectric elements 202 to 212 are not in direct contact with each other, and a lower surface of the support member 214 is exposed between the piezoelectric elements 202 to 212.

The first substrate 222 surrounds the void 226 together with the structure 220. An upper surface of the first substrate 222 is patterned, and a part (protrusion) of the upper surface of the first substrate 222 is joined to a part of a main surface (lower surface) of the structure 220 other than a part 220 a, so as to cause the part 220 a of the lower surface of the structure 220 to face the void 226. Here, the part of the structure 220 joined to the first substrate 222 is the lower surface of the support member 214. Moreover, the second substrate 224 surrounds the pump chamber 230 together with the structure 220, and has a part of its lower surface joined to a part of an upper surface of the support member 214. In this way, the structure 220 including the support member 214 is fixed by being sandwiched between the first substrate 222 and the second substrate 224.

The second substrate 224 is provided with the first opening 250 and the second opening 252 passing through in its thickness direction. These openings are communicated with the pump chamber 230. The lower surface of the second substrate 224 is patterned so as to be in mirror symmetry with the upper surface of the first substrate 222. Note here that the second substrate 224 also has protrusions 224 a to 224 e which protrude downward, so as to partition the pump chamber 230 for each of the piezoelectric elements 202 to 212. When the piezoelectric pump 200 is not in operation, lower surfaces of these protrusions 224 a to 224 e are in direct contact with the upper surface of the support member 214, thereby partitioning the pump chamber 230. That is, the pump chamber 230 has partial pump chambers 232, 234, 236, 238, 240, and 242 respectively for the piezoelectric elements 202 to 212.

Wires 202 d to 212 d are led out respectively from the lower electrodes 202 a to 212 a included in the six piezoelectric elements 202 to 212 in units of two wires, and wires 202 e to 212 e are led out respectively from the upper electrodes 202 c to 212 c included in the six piezoelectric elements 202 to 212 in units of one wire. These led-out wires 202 d to 212 d and 202 e to 212 e extend to terminals 260, and are connected to a power supply (not illustrated) via the terminals 260. Here, the connection parts between the pair of electrodes and the corresponding wires are arranged in an order of the connection part between the lower electrode and the wire, the connection part between the upper electrode and the wire, and the connection part between the lower electrode and the wire, along the fluid flow direction from upstream. For example, in the case of connection parts 202 f and 202 h between the lower electrode 202 a and the two wires 202 d and a connection part 202 g between the upper electrode 202 c and the wire 202 e, the connection parts 202 f, 202 g, and 202 h are arranged in this order along the fluid flow direction from upstream. The same applies to the other connection parts (204 f to 204 h, 206 f to 206 h, 208 f to 208 h, 210 f to 210 h, and 212 f to 212 h).

For instance, such a piezoelectric pump 200 is manufactured in the following manner.

First, the lower electrodes 202 a to 212 a, the piezoelectric bodies 202 b to 212 b, and the upper electrodes 202 c to 212 c are laminated on a film formation substrate in this order. In more detail, first a layer for forming the lower electrodes 202 a to 212 a is formed on a surface of the film formation substrate by, for example, sputtering, CVD, or vapor deposition. The film formation substrate is not specifically limited so long as the layer for forming the lower electrodes 202 a to 212 a can be formed on its surface, and may be a substrate used for normal thin film formation. Preferably, the film formation substrate is a Si substrate. A material of the layer for forming the lower electrodes 202 a to 212 a is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The layer for forming the lower electrodes 202 a to 212 a may have a thickness of 0.05 μm to 1.0 μm, as an example.

Next, the layer for forming the lower electrodes 202 a to 212 a is patterned to a desired shape. A method of the patterning is not specifically limited. As an example, after forming a mask resist on a surface of the layer for forming the lower electrodes as an etch mask, a part of the layer not covered by the mask resist is removed by etching, and then the mask resist is removed. As a result, the lower electrodes 202 a to 212 a are obtained.

Next, the piezoelectric bodies 202 b to 212 b are formed on surfaces of the lower electrodes 202 a to 212 a. A method of forming the piezoelectric bodies 202 b to 212 b may be sputtering, CVD, or vapor deposition. A material of the piezoelectric bodies 202 b to 212 b is not specifically limited so long as it is a piezoelectric material capable of thin film formation. For example, PZT, barium titanate, and the like are applicable. PZT (lead zirconate titanate) is particularly preferable as it has excellent piezoelectric properties and also is easily available. The piezoelectric bodies 202 b to 212 b may have a thickness of 0.5 μm to 5.0 μm, as an example.

Following this, the upper electrodes 202 c to 212 c are formed on surfaces of the piezoelectric bodies 202 b to 212 b by, for example, sputtering, CVD, or vapor deposition. A material of the upper electrodes 202 c to 212 c is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The upper electrodes 202 c to 212 c may have a thickness of 0.05 μm to 1.0 μm, as an example.

For instance, the piezoelectric bodies 202 b to 212 b and the upper electrodes 202 c to 212 c may be formed in such a manner that, after forming a resist of a predetermined shape on the lower electrodes 202 a to 212 a, the piezoelectric bodies 202 b to 212 b and the upper electrodes 202 c to 212 c are formed in this order, and then the resist is removed. Thus, the piezoelectric elements 202 to 212 in which the lower electrodes 202 a to 212 a, the piezoelectric bodies 202 b to 212 b, and the upper electrodes 202 c to 212 c are laminated on the film formation substrate in this order is obtained.

Next, a layer for forming the support member 214 is formed so as to cover the piezoelectric elements 202 to 212. A material of this layer is an insulating material, and preferably a flexible material since the layer needs to bend according to the displacement of the piezoelectric bodies 202 b to 212 b without being damaged. When a flexible material is employed as the material of the layer for forming the support member 214, the displacement of the piezoelectric bodies 202 b to 212 b can be favorably transmitted to the pump chamber 230, which enhances the efficiency of the piezoelectric pump 200. In detail, the material of the layer for forming the support member 214 is preferably a resin material. In this case, first a resin composition (for example, a mixture of a solvent and a resin and/or a monomer) which is a raw material of the resin material is applied onto the surfaces of the film formation substrate and piezoelectric elements 202 to 212. The applied resin composition is then solidified by drying or the like, or hardened by heating, optical irradiation, or the like. After this, the resin composition hardened according to need is patterned to a desired shape. The patterning may be performed using a known method of patterning a resin material. For example, a photolithography method is applicable. As the resin material, a material that favorably adheres to the film formation substrate and the piezoelectric elements 202 to 212 and also has favorable patterning properties such as developability is preferable. For example, a silicone resin, polyimide, parylene, and the like are applicable. Thus, the structure 220 including the piezoelectric elements 202 to 212 and the support member 214 formed on the film formation substrate is obtained.

Aside from the above-mentioned structure 220, the second substrate 224 is made. For instance, the second substrate 224 is obtained from a glass substrate or a ceramic substrate having a thickness of 0.2 mm to 2.0 mm. A surface of the substrate is processed (patterned) to a predetermined shape by etching or the like. Further, the first opening 250 and the second opening 252 are formed through the substrate in its thickness direction by etching or the like, at predetermined positions. In this way, the second substrate 224 that has the openings 250 and 252 and whose lower surface is patterned to the predetermined shape is obtained.

Next, the second substrate 224 is attached onto the above-mentioned structure 220. Here, having positioned the structure 220 and the second substrate 224 so as to make the patterned lower surface of the second substrate 224 face the surface of the structure 220 where the support member 214 is formed and also to form the pump chamber 230, the lower surface of the second substrate 224 and the support member 214 are joined by being attached to each other around an area corresponding to the pump chamber 230. Meanwhile, the protrusions 224 a to 224 e of the second substrate 224 are in direct contact with the upper surface of the support member 214 but are not joined to the upper surface of the support member 214. A method of the attachment may be a method of applying, for example, an adhesive to an area of contact between the support member 214 and the second substrate 224. Subsequently, the film formation substrate is peeled and removed by etching or the like. Thus, a complex including the structure 220 and the second substrate 224 is obtained.

Aside from the above-mentioned complex, the first substrate 222 is made. For instance, the first substrate 222 is obtained from a glass substrate or a ceramic substrate having a thickness of 0.2 mm to 2.0 mm. A surface of the substrate is processed (patterned) to a predetermined shape by etching or the like. As a result, the first substrate 222 is obtained.

Next, the first substrate 222 is attached to a surface of the above-mentioned complex where the structure 220 is provided. Here, having positioned the first substrate 222 and the complex so as to make the patterned surface of the first substrate 222 face a surface of the structure 220 where the piezoelectric elements 202 to 212 are formed and also to form the void 226, the first substrate 222 and the surface of the structure 220 are joined by being attached to each other. A method of the attachment may be a method of applying, for example, an adhesive to an area of contact between the support member 214 and the first substrate 222. As a result, the piezoelectric pump 200 of this embodiment is obtained.

Thus, the piezoelectric pump 200 of this embodiment is manufactured on the basis of the so-called thin film process. This makes it possible to suppress a variation in quality, enhance a yield, and reduce manufacturing costs.

The following describes a method of operating the piezoelectric pump 200 of this embodiment, with reference to FIG. 7. First, in a step (A), the piezoelectric pump 200 is in a stopped state, and the pump chambers 232 to 242 are partitioned from each other by the protrusions 224 a to 224 e. Next, in a step (B), a voltage is applied between the lower electrode 202 a of the piezoelectric element 202 from the wire 202 d via the connection part 202 h and the upper electrode 202 c of the piezoelectric element 202 from the wire 202 e via the connection part 202 g, and at the same time a voltage is applied between the lower electrode 204 a of the piezoelectric element 204 from the wire 204 d via the connection part 204 f and the upper electrode 204 c of the piezoelectric element 204 from the wire 204 e via the connection part 204 g. As a result, the displacement of the piezoelectric bodies 202 b and 204 b causes the piezoelectric elements 202 and 204 to simultaneously bend downward together with the support member 214. With this bend, the support member 214 situated between the piezoelectric elements 202 and 204 is pulled downward, and the protrusion 224 a and the support member 214 separate from each other. This induces a negative pressure in the pump chambers 232 and 234, and accordingly the piezoelectric pump 200 sucks the fluid from the first opening 250 into these pump chambers 232 and 234. Note that the top of the bent piezoelectric element 202 is a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 202 h and the connection part 202 g than to a central part in the in-plane direction, and the top of the bent piezoelectric element 204 is a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 204 f and the connection part 204 g than to a central part in the in-plane direction.

Next, in a step (C), the voltage application between the lower electrode 202 a and the upper electrode 202 c is stopped, and a voltage is applied between the lower electrode 204 a of the piezoelectric element 204 from the wire 204 d via the connection part 204 h and the upper electrode 204 c of the piezoelectric element 204 from the wire 204 e via the connection part 204 g, and at the same time a voltage is applied between the lower electrode 206 a of the piezoelectric element 206 from the wire 206 d via the connection part 206 f and the upper electrode 206 c of the piezoelectric element 206 from the wire 206 e via the connection part 206 g. As a result, the piezoelectric element 202 returns to the stopped state and the protrusion 224 a and the support member 214 come into direct contact again between the piezoelectric elements 202 and 204, while the displacement of the piezoelectric body 206 b causes the piezoelectric element 206 to bend downward together with the support member 214. With this bend, the support member 214 situated between the piezoelectric elements 204 and 206 is pulled downward, and the protrusion 224 b and the support member 214 separate from each other. This pressurizes the pump chamber 232 and also induces a negative pressure in the pump chamber 236, and accordingly the piezoelectric pump 200 pushes the fluid out of the pump chamber 232 while sucking the fluid into the pump chamber 236, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 204 a is switched from via the connection part 204 f to via the connection part 204 h, the top of the bent piezoelectric element 204 changes from the part that is slightly closer to the imaginary connection part at the intermediate point between the connection part 204 f and the connection part 204 g than to the central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 204 h and the connection part 204 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 204 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 234 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

Following this, in a step (D), the voltage application between the lower electrode 204 a and the upper electrode 204 c is stopped, and a voltage is applied between the lower electrode 206 a of the piezoelectric element 206 from the wire 206 d via the connection part 206 h and the upper electrode 206 c of the piezoelectric element 206 from the wire 206 e via the connection part 206 g, and at the same time a voltage is applied between the lower electrode 208 a of the piezoelectric element 208 from the wire 208 d via the connection part 208 f and the upper electrode 208 c of the piezoelectric element 208 from the wire 208 e via the connection part 208 g. As a result, the piezoelectric element 204 returns to the stopped state and the protrusion 224 b and the support member 214 come into direct contact again between the piezoelectric elements 204 and 206, while the displacement of the piezoelectric body 208 b causes the piezoelectric element 208 to bend downward together with the support member 214. With this bend, the support member 214 situated between the piezoelectric elements 206 and 208 is pulled downward, and the protrusion 224 c and the support member 214 separate from each other. This pressurizes the pump chamber 234 and also induces a negative pressure in the pump chamber 238, and accordingly the piezoelectric pump 200 pushes the fluid out of the pump chamber 234 while sucking the fluid into the pump chamber 238, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 206 a is switched from via the connection part 206 f to via the connection part 206 h, the top of the bent piezoelectric element 206 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 206 f and the connection part 206 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 206 h and the connection part 206 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 206 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 236 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

Next, in a step (E), the voltage application between the lower electrode 206 a and the upper electrode 206 c is stopped, and a voltage is applied between the lower electrode 208 a of the piezoelectric element 208 from the wire 208 d via the connection part 208 h and the upper electrode 208 c of the piezoelectric element 208 from the wire 208 e via the connection part 208 g, and at the same time a voltage is applied between the lower electrode 210 a of the piezoelectric element 210 from the wire 210 d via the connection part 210 f and the upper electrode 210 c of the piezoelectric element 210 from the wire 210 e via the connection part 210 g. As a result, the piezoelectric element 206 returns to the stopped state and the protrusion 224 c and the support member 214 come into direct contact again between the piezoelectric elements 206 and 208, while the displacement of the piezoelectric body 210 b causes the piezoelectric element 210 to bend downward together with the support member 214. With this bend, the support member 214 situated between the piezoelectric elements 208 and 210 is pulled downward, and the protrusion 224 d and the support member 214 separate from each other. This pressurizes the pump chamber 236 and also induces a negative pressure in the pump chamber 240, and accordingly the piezoelectric pump 200 pushes the fluid out of the pump chamber 236 while sucking the fluid into the pump chamber 240, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 208 a is switched from via the connection part 208 f to via the connection part 208 h, the top of the bent piezoelectric element 208 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 208 f and the connection part 208 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 208 h and the connection part 208 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 208 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 238 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

After this, in a step (F), the voltage application between the lower electrode 208 a and the upper electrode 208 c is stopped, and a voltage is applied between the lower electrode 210 a of the piezoelectric element 210 from the wire 210 d via the connection part 210 h and the upper electrode 210 c of the piezoelectric element 210 from the wire 210 e via the connection part 210 g, and at the same time a voltage is applied between the lower electrode 212 a of the piezoelectric element 212 from the wire 212 d via the connection part 212 f and the upper electrode 212 c of the piezoelectric element 212 from the wire 212 e via the connection part 212 g. As a result, the piezoelectric element 208 returns to the stopped state and the protrusion 224 d and the support member 214 come into direct contact again between the piezoelectric elements 208 and 210, while the displacement of the piezoelectric body 212 b causes the piezoelectric element 212 to bend downward together with the support member 214. With this bend, the support member 214 situated between the piezoelectric elements 210 and 212 is pulled downward, and the protrusion 224 e and the support member 214 separate from each other. This pressurizes the pump chamber 238 and also induces a negative pressure in the pump chamber 242, and accordingly the piezoelectric pump 200 pushes the fluid out of the pump chamber 238 while sucking the fluid into the pump chamber 242, thereby discharging the fluid from the second opening 252. Moreover, because the voltage application to the lower electrode 210 a is switched from via the connection part 210 f to via the connection part 210 h, the top of the bent piezoelectric element 210 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 210 f and the connection part 210 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 210 h and the connection part 210 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 210 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 240 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

By repeating the steps described above, it is possible to transfer the fluid through the piezoelectric pump 200 of this embodiment. In this case, for example the above-mentioned step (B) may be started at the same time as the start of the above-mentioned step (E). By doing so, the fluid transferring amount per unit time by the piezoelectric pump 200 can be further increased.

The piezoelectric pump 200 of this embodiment sequentially applies voltages to the piezoelectric elements 202 to 212 in units of two piezoelectric elements, from upstream to downstream in the fluid flow direction. This causes the piezoelectric elements 202 to 212 to move in a peristaltic manner as a whole, to transfer the fluid. A thin-film piezoelectric element typically has a small pump volume and also does not exhibit a large amount of displacement, so that an internal pressure of a pump chamber cannot be increased significantly. This makes it difficult to increase the fluid flow amount. According to the piezoelectric pump 200 of this embodiment, however, the fluid is transferred by operating the plurality of piezoelectric elements 202 to 212 in a peristaltic manner as a whole, as described above. Thus, even when the fluid transferring amount per piezoelectric element is small, the transferring amount of the piezoelectric pump 200 as a whole can be increased by simultaneously operating the plurality of piezoelectric elements. In particular, by returning an upstream piezoelectric element from a downward bent state to an original state to pressurize a corresponding pump chamber and at the same time bending a downstream piezoelectric element downward to depressurize a corresponding pump chamber, a large transferring amount can be achieved with a smaller voltage. Hence the piezoelectric pump 200 has extremely high efficiency.

Furthermore, in the piezoelectric pump 200 of this embodiment, each of the pump chambers 232 to 242 is surrounded by the second substrate 224 and the structure 220, so that the displacement of each of the piezoelectric elements 202 to 212 in the pump chambers 232 to 242 can be efficiently converted to compression (pressurization) and expansion (depressurization) of the fluid. Besides, the fluid is movable from the pump chambers 232 to 240 respectively to the pump chambers 234 to 242 adjacent on the downstream side. Accordingly, the above-mentioned compression and expansion can be efficiently converted to the transfer of the fluid between the pump chambers. Further, while the structure 220 is firmly fixed by being sandwiched between the first substrate 222 and the second substrate 224, the void 226 permits the movement of the structure 220 in the thickness direction and particularly the flex of the structure 220 toward the first substrate 222. As a result, the piezoelectric pump 200 can convert the voltage applied to each of the piezoelectric elements 202 to 212 to the fluid transferring amount more efficiently.

Moreover, in the piezoelectric pump 200 of this embodiment, each of the piezoelectric elements 202 to 212 includes one pair of electrodes (lower electrode, upper electrode). The size of each of the piezoelectric elements 202 to 212 is not large with respect to these electrodes, and the range of bend of the electrodes with the displacement of each of the piezoelectric elements 202 to 212 is not large. Therefore, the piezoelectric pump 200 can adequately suppress electrode peeling. In addition, the piezoelectric pump 200 of this embodiment includes the six piezoelectric elements 202 to 212 supported by the single support member 214, where the voltage applied to any of the piezoelectric elements does not affect the displacement of the other piezoelectric elements. Accordingly, the piezoelectric pump 200 can operate with sufficient stability in high speed driving, and also adequately suppress a variation in displacement amount of the piezoelectric elements.

Furthermore, in the piezoelectric pump 200 of this embodiment, the piezoelectric elements 202 to 212 are sandwiched between the first substrate 222 and the second substrate 224 and so are in a state of not being directly exposed to outside, and the void 226 is present around the piezoelectric elements 202 to 212. Though the piezoelectric elements 202 to 212 are a source of vibration, the vibration is absorbed by the void 226 in the piezoelectric pump 200 of this embodiment, because the piezoelectric elements 202 to 212 are not directly exposed to outside. Consequently, the piezoelectric pump 200 can suppress the propagation of the vibration by the piezoelectric elements 202 to 212 to outside, and also suppress signal noise associated with the vibration. Furthermore, the piezoelectric pump 200 has a construction in which the piezoelectric elements 202 to 212 are not provided outside the first substrate 222 and the second substrate 224 but sandwiched between the first substrate 222 and the second substrate 224. This allows circuits and elements other than the piezoelectric elements 202 to 212 constituting the piezoelectric pump 200 to be provided outside the first substrate 222 and the second substrate 224. Hence an electronic component including the piezoelectric pump 200 can be integrated with higher density.

In the piezoelectric pump 200 of this embodiment, the part 214 a of one main surface of the support member 214 facing the pump chamber 230 has a planar shape where six circular surfaces put in a row are partially overlapped with each other at their peripheries, and each of the piezoelectric elements 202 to 212 has a circular main surface. Typically, when a voltage is applied to a thin-film piezoelectric element, the piezoelectric element is displaced in the thickness direction (d33 direction) and also displaced radially in the in-plane direction (d31 direction). This being so, the use of the above-mentioned piezoelectric elements 202 to 212 and support member 214 enables the radial displacement to be efficiently reflected on the piezoelectric element bend. Further, a large portion of the lower surface of each of the pump chambers 232 to 242 is occupied by the corresponding one of the piezoelectric elements 202 to 212, thereby reducing dead spaces. Accordingly, the flow of the fluid in the entire pump chambers 232 to 242 can be easily induced by the bend of the piezoelectric elements 202 to 212. Hence the piezoelectric pump 200 can convert the applied voltage to the fluid transferring amount more efficiently.

In addition, in the piezoelectric pump 200 of this embodiment, the top of one bent piezoelectric element can be moved downstream, by arranging the connection parts between the electrodes and the wires in the above-mentioned manner. This facilitates the transfer of the fluid downstream, so that the applied voltage can be converted to the fluid transferring amount more efficiently.

Moreover, in the piezoelectric pump 200 of this embodiment, in the case where a Pb (lead) containing material such as PZT is adopted as the material of the piezoelectric bodies 202 b to 212 b, Pb generated from the piezoelectric bodies 202 b to 212 b can be prevented from scattering to outside the piezoelectric pump 200, because the piezoelectric bodies 202 b to 212 b are surrounded by the first substrate 222 and the support member 214.

Furthermore, the piezoelectric pump 200 of this embodiment employs the thin-film piezoelectric elements 202 to 212 which are displaced by a low voltage, so that favorable efficiency can be exhibited even with a lower voltage. In addition, by making the piezoelectric elements 202 to 212 in thin film form, a piezoelectric pump of an optimum shape in accordance with design can be manufactured when compared with the so-called bulk-type piezoelectric pump. Further, by employing the thin-film piezoelectric elements 202 to 212, the piezoelectric pump can be made more compact and thinner, when compared with the bulk-type piezoelectric pump. This enables an electronic component including the piezoelectric pump 200 to be integrated with higher density, thereby lending itself to effective use for a product that applies MEMS technology.

FIG. 9 is a process chart schematically showing a manufacturing method of a piezoelectric pump 470 in a third embodiment of the present invention. First, in a step (A1), a lower electrode layer 404, a piezoelectric body layer 406, and an upper electrode layer 408 are laminated on a first substrate 402 which also functions as a film formation substrate, in this order. In more detail, first the lower electrode layer 404 is formed on a surface of the first substrate 402 by, for example, sputtering, CVD, or vapor deposition, to join the lower electrode layer 404 to the first substrate 402. The first substrate 402 is not specifically limited so long as the lower electrode layer 404 and the piezoelectric body layer 406 can be formed on its surface, and may be a substrate used for normal thin film formation. In view of the combination with a material and a film formation method of the piezoelectric body layer 406 described later and in view of obtaining a highly-oriented piezoelectric body, however, the first substrate 402 is preferably a Si substrate. A material of the lower electrode layer 404 is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The lower electrode layer 404 has a thickness of 0.05 μm to 1.0 μm, as an example.

Next, the piezoelectric body layer 406 is formed on a surface of the lower electrode layer 404, and on an exposed surface of the first substrate 402 according to need. A formation method of the piezoelectric body layer 406 may be sputtering, CVD, vapor deposition, or the like, but a film formation method using epitaxial growth on a Si substrate is particularly preferable because a piezoelectric body with high orientation and excellent piezoelectric properties can be obtained and also a manufacturing yield of the piezoelectric pump 470 can be improved. For instance, such a film formation method is disclosed in Japanese Patent Application Laid-Open No. 2000-332569 by the applicant of this application. A material of the piezoelectric body layer 406 is not specifically limited so long as it is a piezoelectric material capable of thin film formation. For example, PZT, barium titanate, and the like are applicable. PZT (lead zirconate titanate) is particularly preferable as it has excellent piezoelectric properties and also is easily available. In the case of using PZT as the material of the piezoelectric body layer 406 and forming the piezoelectric body layer 406 on the Si substrate by the film formation method using epitaxial growth, it is preferable to form a PZT (001) thin film on Si (100) by epitaxial growth, in view of obtaining especially excellent orientation. The piezoelectric body layer 406 has a thickness of 0.5 μm to 5.0 μm, as an example.

Following this, the upper electrode layer 408 is formed on a surface of the piezoelectric body layer 406 by, for example, sputtering, CVD, or vapor deposition. A material of the upper electrode layer 408 is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The upper electrode layer 408 may have a thickness of 0.05 μm to 1.0 μm, as an example.

Next, in a step (A2), the lower electrode layer 404, the piezoelectric body layer 406, and the upper electrode layer 408 laminated in the above-mentioned manner are patterned to a desired shape. A method of the patterning is not specifically limited. As an example, after forming a mask resist on a surface of the upper electrode layer 408 as an etch mask, a part of each of the above-mentioned layers not covered by the mask resist is removed by etching, and then the mask resist is removed. As an alternative patterning method, a liftoff method of performing resist patterning, film formation, and unwanted part removal may be used. As a result, piezoelectric elements 420 each including a lower electrode 414, a piezoelectric body 416, and an upper electrode 418 which are laminated in this order are obtained in a state of being joined to the first substrate 402. Here, in addition to or instead of the steps (A1) and (A2), the lower electrode layer 404, the piezoelectric body layer 406, and the upper electrode layer 408 may be directly patterned along with film formation by, for example, laser writing. The piezoelectric elements 420 may be obtained by repeatedly performing film formation and patterning for each layer.

For example, the piezoelectric elements 420 formed by patterning have a planar shape as shown in FIG. 10. FIG. 10 is a schematic view showing the planar shape of the piezoelectric elements 420 and a part of the first substrate 402 removed by etching described later. As shown in FIG. 10B, when the piezoelectric elements 420 have a planar shape with a constriction 420 a, the piezoelectric elements 420 can be displaced to a large extent by application of a small voltage, which contributes to an increase in fluid flow amount. However, the piezoelectric elements 420 may instead have a planar shape with no constriction, as shown in FIG. 10A.

Alternatively, the piezoelectric elements 420 may have a planar shape whose constriction is gradually tapered toward an electrode lead-out part in its in-plane direction, as shown in FIG. 10C. The piezoelectric elements 420 may instead have a circular planar shape, as shown in FIG. 10D. Furthermore, the piezoelectric body 416 and each of the electrodes 414 and 418 in each piezoelectric element 420 may have the same planar shape or different planar shapes. For example, in FIGS. 10A and 10B, the piezoelectric body 416 and each of the electrodes 414 and 418 have substantially the same planar shape. On the other hand, each of the electrodes 414 and 418 may have a planar shape that adds a protrusion part 420 b to the piezoelectric body 416, as shown in FIGS. 10C and 10D. This protrusion part 420 b can also function as a lead-out part of each of the electrodes 414 and 418. In the case of FIGS. 10C and 10D, the piezoelectric elements 420 may be obtained through a process of formation and patterning of the lower electrode layer 404, formation and patterning of the piezoelectric body layer 406, and formation and patterning of the upper electrode layer 408, instead of the steps (A1) and (A2).

Note that the piezoelectric elements 420 may have a constriction in their thickness direction, in addition to or instead of in the in-plane direction of the support member. The shape of the constriction may be changed appropriately in order to control the displacement in the in-plane direction and the displacement in the thickness direction in a well balanced manner, according to the type of the fluid transferred.

Next, in a step (A3), an insulating member 422 is formed on surfaces of the first substrate 402 and the piezoelectric elements 420. The insulating member 422 is a member that constitutes a support member of the piezoelectric pump. A material of the insulating member 422 is an insulating material, and preferably a flexible material since the insulating member 422 needs to bend appropriately according to the displacement of the piezoelectric elements 420 without being damaged. When a flexible material is employed as the material of the insulating member 422, the displacement of the piezoelectric elements 420 can be favorably transmitted to a pump chamber, which contributes to enhanced efficiency (fluid transferring efficiency, operation efficiency) of the piezoelectric pump. In detail, the material of the insulating member 422 is preferably a resin material. In the case where the material of the insulating member 422 is a resin material, the step (A3) is performed as follows. First, a resin composition (for example, a mixture of a solvent and a resin and/or a monomer) which is a raw material of the resin material is applied onto the surfaces of the first substrate 402 and piezoelectric elements 420. After the applied resin composition is solidified by drying or the like or hardened by heating, optical irradiation, or the like, the resin composition is patterned to a desired shape. The patterning may be performed using a known method of patterning a resin material. For example, a photolithography method is applicable. As the resin material, a material that favorably adheres to the first substrate 402 and the piezoelectric elements 420 and also has favorable patterning properties such as developability is preferable. For example, a silicone resin, polyimide, parylene, and the like are applicable. A surface shape of the insulating member 422 obtained by patterning may be any shape suitable as a wall surface forming the pump chamber of the piezoelectric pump. Thus, a structure 424 including the piezoelectric elements 420 and the insulating member 422 which supports the piezoelectric elements 420 is obtained.

Next, in a step (A4), the first substrate 402 is partially etched. This step (A4) is described in detail below, by referring again to FIG. 10 as well as FIG. 9. In the step (A4), a part of the first substrate 402 facing the piezoelectric elements 420 and a part of the first substrate 402 facing a part of the insulating member 422 which surrounds the periphery of each piezoelectric element 420 are removed by etching, to form an opening 412. In FIG. 10, an area enclosed by a dashed-dotted line is the opening 412 of the first substrate 402. This causes a part of a surface of each piezoelectric element 420 facing the first substrate 402 and a part of a surface of the insulating member 422 facing the first substrate 402, to be exposed. The part of each piezoelectric element 420 where the surface is exposed functions as a displacement part 420 c, and the part of each piezoelectric element 420 where the surface is not exposed functions as a fixed part 420 d, as described later. Moreover, the part of the insulating member 422 where the surface is exposed is a surrounding part 422 a that surrounds the displacement part 420 c of each piezoelectric element 420, and can expand/contract and bend with the displacement of the piezoelectric element 420.

A method of the etching is not specifically limited. As an example, after forming a mask resist of a predetermined shape on the surface of the first substrate 402 as an etch mask, a part of the first substrate 402 not covered by the mask resist is removed by etching, and then the mask resist is removed. As an alternative etching method, a liftoff method of performing resist patterning, film formation, and unwanted part removal may be used. The etching is preferably dry etching. Examples include reactive gas etching, reactive ion etching, reactive ion beam etching, ion beam etching, and reactive laser beam etching. As a result, a first complex 426 including the first substrate 402 with the opening 412 and the piezoelectric elements 420 and the insulating member 422 formed by being joined to the first substrate 402, is obtained.

Meanwhile, in a step (B1), first a material substrate 430 is prepared. For example, the material substrate 430 is a glass substrate or a ceramic substrate, and has a thickness of 0.2 mm to 2.0 mm. Following this, in a step (B2), a surface of the material substrate 430 is processed to a predetermined shape by etching or the like. Further, in a step (B3), a first opening 430 a and a second opening 430 b are formed through the material substrate 430 in its thickness direction by etching or the like, at predetermined positions. Thus, a second substrate 432 having the openings 430 a and 430 b is obtained. Here, a surface shape of the second substrate 432 obtained by processing may be any shape suitable as a wall surface forming the pump chamber of the piezoelectric pump.

Next, in a step (C), the second substrate 432 is attached to a surface of the first complex 426 where the insulating member 422 is formed. When doing so, positioning is performed so that the surface of the second substrate 432 processed by etching or the like faces the first complex 426 and also the openings 430 a and 430 b are communicated with the pump chamber of the piezoelectric pump. A method of the attachment may be a method of applying, for example, an adhesive or a resin to an area of contact between the first complex 426 and the second substrate 432. Thus, the piezoelectric pump 470 of this embodiment is obtained.

The obtained piezoelectric pump 470 of this embodiment includes: the structure 424 including the plurality of piezoelectric elements 420 and the insulating member 422 which is the support member that supports the plurality of piezoelectric elements 420; and the first substrate 402 and the second substrate 432 that directly sandwich the structure 424, and has: a pump chamber 478 surrounded by the second substrate 432 and the structure 424; and the first opening 430 a and the second opening 430 b that are communicated with the pump chamber 478. Each piezoelectric element 420 includes the displacement part 420 c which is displaced by application of a voltage, and the fixed part 420 d which is fixed by being sandwiched between the first substrate 402 and the second substrate 432. The insulating member 422 has the surrounding part 422 a that surrounds the periphery of the displacement part 420 c of each piezoelectric element 420. Surfaces of the displacement part 420 c and the surrounding part 422 a on the first substrate 402 side are exposed. Moreover, the first substrate 402 has the opening 412 formed by removing the part facing the displacement part 420 c and the surrounding part 422 a.

In more detail, the structure 424 included in the piezoelectric pump 470 of this embodiment includes the plurality of piezoelectric elements 420, and the insulating member 422 that is directly joined to the plurality of piezoelectric elements 420 to support the plurality of piezoelectric elements 420. The insulating member 422 has a film part 422 b joined to the surface of each piezoelectric element 420 facing the second substrate 432, and a peripheral part 422 c surrounding the thin film part and each piezoelectric element 420. A portion of the peripheral part 422 c where the surface is exposed to the first substrate 402 is the surrounding part 422 a. Each piezoelectric element 420 is in thin film form and is disposed so as to be embedded at a lower side of the film part 422 b of the insulating member 422. Each piezoelectric element 420 and the insulating member 422 are joined so that the insulating member 422 covers the surface of the piezoelectric element 420 facing the pump chamber (flow path) 478.

An upper surface of the first substrate 402 is joined to a lower surface of a non-motion part of the structure 424. Meanwhile, the second substrate 432 may contact a part of the insulating member 422 forming the pump chamber 478 in a state where the piezoelectric pump 470 is not in operation, but is not joined to the part of the insulating member 422 forming the pump chamber 478. The second substrate 432 has the first opening 430 a and the second opening 430 b passing through in the thickness direction, and the first opening 430 a and the second opening 430 b are communicated with the pump chamber 478. A part of the plurality of piezoelectric elements 420 is positioned below each of the openings 430 a and 430 b of the second substrate 432. When the piezoelectric pump 470 is not in operation, the film part 422 b of the insulating member 422 situated between the openings 430 a and 430 b and the corresponding piezoelectric elements 420 block the openings 430 a and 430 b.

The following describes a method of operating the piezoelectric pump 470 of this embodiment. In the piezoelectric pump 470 of this embodiment, when a voltage is applied to the thin-film piezoelectric body 416, the corresponding piezoelectric element 420 is displaced in the in-plane direction (d31 direction) and the thickness direction (d33 direction). In particular, since the piezoelectric element 420 is in thin film form and also the peripheral part of the structure 424 is fixed by the first substrate 402 and the second substrate 432, the piezoelectric element 420 bends in the thickness direction according to the displacement of the piezoelectric body 416 in the in-plane direction. By switching the voltage application between ON and OFF or switching a direction of the applied voltage between forward and backward (applying an alternating-current voltage), the structure 424 repeatedly moves up and down in the thickness direction, with the peripheral part of the structure 424 fixed by the first substrate 402 and the second substrate 432 as a fulcrum. This operation changes the volume and internal pressure of the pump chamber 478 that also functions as the flow path, as a result of which the fluid is transferred in the piezoelectric pump 470 through the first opening 430 a, the pump chamber 478, and the second opening 430 b in this order.

The operation method of the piezoelectric pump 470 of this embodiment is described in more detail below, with reference to FIG. 11. First, in a step (A), the piezoelectric pump 470 is in a stopped state, and the upper surface of the structure 424 is in contact with the second substrate 432. Therefore, the openings 430 a and 430 b are blocked by the insulating member 422 forming the pump chamber 478. Next, in a step (B), a voltage is applied to a most upstream piezoelectric element 420 x of the plurality of piezoelectric elements 420. As a result, the displacement of the piezoelectric body 416 in the piezoelectric element 420 x causes the piezoelectric element 420 x to bend downward together with the insulating member 422. With this bend, the insulating member 422 is pulled downward and separates from the second substrate 432. Accordingly, a negative pressure is induced in the pump chamber 478, and the pump chamber 478 is communicated with outside via the first opening 430 a. Hence the piezoelectric pump 470 sucks the fluid from the first opening 430 a into the pump chamber 478.

Next, in a step (C), a voltage is applied to a midstream piezoelectric element 420 y, while stopping the voltage application to the most upstream piezoelectric element 420 x. As a result, the displacement of the piezoelectric body 416 in the piezoelectric element 420 y causes the piezoelectric element 420 y to bend downward together with the insulating member 422. With this bend, the insulating member 422 is pulled downward and separates from the second substrate 432. Meanwhile, the piezoelectric element 420 x returns to the stopped state, thereby making the insulating member 422 contact the second substrate 432 again and blocking the first opening 430 a. Accordingly, a part of the pump chamber 478 above the piezoelectric element 420 x is pressurized whilst a negative pressure is induced in a part of the pump chamber 478 above the piezoelectric element 420 y, so that the piezoelectric pump 470 pushes the fluid in the pump chamber 478 downstream. Moreover, since the first opening 430 a is blocked, the suction of the fluid from outside is temporarily stopped.

Following this, in a step (D), a voltage is applied to a most downstream piezoelectric element 420 z, while stopping the voltage application to the midstream piezoelectric element 420 y. As a result, the displacement of the piezoelectric body 416 in the piezoelectric element 420 z causes the piezoelectric element 420 z to bend downward together with the insulating member 422. With this bend, the insulating member 422 is pulled downward and separates from the second substrate 432. Meanwhile, the piezoelectric element 420 y returns to the stopped state, thereby making the insulating member 422 contact the second substrate 432 again. Accordingly, the part of the pump chamber 478 above the piezoelectric element 420 y is pressurized whilst a negative pressure is induced in a part of the pump chamber 478 above the piezoelectric element 420 z, so that the piezoelectric pump 470 pushes the fluid in the pump chamber 478 further downstream. Moreover, since the pump chamber 478 is communicated with outside via the second opening 430 b, the piezoelectric pump 470 discharges the fluid from the pump chamber 478 to outside via the second opening 430 b.

By repeating the steps described above, it is possible to transfer the fluid through the piezoelectric pump 470 of this embodiment. In this case, for example the above-mentioned step (B) may be started at the same time as the start of the above-mentioned step (D). By doing so, the fluid transferring amount per unit time by the piezoelectric pump 470 can be further increased.

In the piezoelectric pump 470 of this embodiment, even when a voltage is applied to the piezoelectric element 420, the displacement of the fixed part 420 d in the piezoelectric element 420 is suppressed because the fixed part 420 d is fixed by being directly sandwiched between the first substrate 402 and the second substrate 432. On the other hand, the displacement part 420 c in the piezoelectric element 420 is not sandwiched by the first substrate 402 and the second substrate 432. Accordingly, the piezoelectric element 420 vibrates by the displacement part 420 c displacing favorably with the fixed part 420 d as a fulcrum. As a result, the interference between the motion of the insulating member 422 functioning as a diaphragm and the displacement of the piezoelectric element 420 can be adequately suppressed when compared with the conventional techniques. This enables the piezoelectric pump 470 to transfer the fluid stably.

Furthermore, in the piezoelectric pump 470, from the state where the first substrate 402 is joined to the above-mentioned structure 424, the part of the first substrate 402 facing the displacement part 420 c and the surrounding part 422 a of the insulating member surrounding the periphery of the displacement part 420 c is removed by etching, so as to expose the displacement part 420 c and the surrounding part 422 a. This allows the displacement part 420 c and the surrounding part 422 a to release stress generated due to the restraint of being joined onto the first substrate 402 by vapor deposition or the like. Meanwhile, the other part of the first substrate 402 remains joined to and supported by the structure 424. Thus, the structure 424 can be fixed to the first substrate 402 accurately and reliably. Hence the piezoelectric pump 470 can transfer the fluid more stably.

In the manufacture of the piezoelectric pump 470 of this embodiment, the entire surface of the structure 424 is once joined to the first substrate. Since the piezoelectric pump is mainly formed by a thin film method, each member constituting the structure 424 is joined to another member in a relatively high temperature environment such as vapor deposition or, in the case of the insulating member 422, joined by applying a molten resin. As a result of subsequent cooling, the structure 424 tries to contract, but the stress (distribution) of the structure 424 is uniform at high level since the entire surface is restrained by the first substrate 402. After this, the part of the first substrate 402 joined to the displacement part 420 c of the piezoelectric element 420 and the surrounding part 422 a of the insulating member 422 is removed by etching. Although the displacement part 420 c and the surrounding part 422 a are exposed as a result of this, the other part remains restricted by the joint with the first substrate 402. Accordingly, the stress in the displacement part 420 c and the surrounding part 422 a is maintained uniform at high level, so that the piezoelectric pump 470 can transfer the fluid with sufficient stability and in large flow amount.

In addition, in the piezoelectric pump 470, not only the displacement part 420 c of the piezoelectric element 420 but also the surrounding part 422 a of the insulating member 422 surrounding the displacement part 420 c is exposed. This allows for large movement of these exposed parts, which contributes to an increase in pump volume.

The piezoelectric pump 470 of this embodiment sequentially applies a voltage to the plurality of piezoelectric elements 420 from upstream to downstream in the fluid flow direction. This causes the piezoelectric elements 420 to move in a peristaltic manner (like wriggling) as a whole, to transfer the fluid. A thin-film piezoelectric element typically has a small pump volume and also does not exhibit a large amount of displacement, so that an internal pressure of a pump chamber cannot be increased significantly. This makes it difficult to increase the fluid flow amount. According to the piezoelectric pump 470 of this embodiment, however, the fluid is transferred by operating the plurality of piezoelectric elements 420 in a peristaltic manner as a whole, as described above. Thus, even when the fluid transferring amount per piezoelectric element is small, the transferring amount of the piezoelectric pump 470 as a whole can be increased by simultaneously operating the plurality of piezoelectric elements. In particular, by returning an upstream piezoelectric element from a downward bent state to an original state to pressurize a corresponding part of the pump chamber and at the same time bending a downstream piezoelectric element downward to depressurize a corresponding part of the pump chamber, a large transferring amount can be achieved with a smaller voltage. Hence the piezoelectric pump 470 has extremely high efficiency.

Furthermore, in the piezoelectric pump 470 of this embodiment, the pump chamber 478 is surrounded by the second substrate 432 and the structure 424, so that the displacement of the plurality of piezoelectric elements 420 in the pump chamber 478 can be efficiently converted to compression (pressurization) and expansion (depressurization) of the fluid. Besides, the fluid is movable in the pump chamber 478 from upstream to downstream. Accordingly, the above-mentioned compression and expansion can be efficiently converted to the transfer of the fluid between pump chambers. Further, while the structure 424 is firmly fixed by being sandwiched between the first substrate 402 and the second substrate 432, the movement of the structure 424 in the thickness direction and particularly the flex of the structure 424 toward the first substrate 402 are permitted. As a result, the piezoelectric pump 470 can convert the voltage applied to the piezoelectric elements 420 to the fluid transferring amount more efficiently.

Moreover, in the piezoelectric pump 470 of this embodiment, each of the plurality of piezoelectric elements 420 includes one pair of electrodes (the lower electrode 414 and the upper electrode 418). The size of the piezoelectric element 420 is not large with respect to these electrodes, and the range of bend of the electrodes with the displacement of the piezoelectric element 420 is not large. Therefore, the piezoelectric pump 470 can adequately suppress electrode peeling. In addition, the piezoelectric pump 470 of this embodiment includes the plurality of piezoelectric elements 420 supported by the single insulating member 422, where the voltage applied to any of the piezoelectric elements 420 does not affect the displacement of the other piezoelectric elements 420. Accordingly, the piezoelectric pump 470 can operate with sufficient stability in high speed driving, and also adequately suppress a variation in displacement amount of the piezoelectric elements 420.

Moreover, in the piezoelectric pump 470 of this embodiment, by making the piezoelectric elements 420 in thin film form, a piezoelectric pump of an optimum shape in accordance with design can be manufactured when compared with the so-called bulk-type piezoelectric pump. Further, by employing the thin-film piezoelectric elements 420, the piezoelectric pump can be made more compact and thinner when compared with the bulk-type piezoelectric pump. This enables an electronic component including the piezoelectric pump 470 to be integrated with higher density, thereby lending itself to effective use for a product that applies MEMS technology.

Note that, in the piezoelectric pump 470 of this embodiment, it is preferable that the lower electrode 414, the piezoelectric body 416, and the upper electrode 418 which constitute the piezoelectric element 420 satisfy the following relation. That is, it is preferable that a laminate composed of the lower electrode 414 and the piezoelectric body 416 has a smaller product of Young's modulus and thickness than the upper electrode 418. In other words, when the Young's modulus of the laminate is denoted by E1 (N/m²), the thickness of the laminate is denoted by D1 (nm), the Young's modulus of the upper electrode 418 is denoted by E2 (N/m²), and the thickness of the upper electrode 418 is denoted by D2 (nm), it is preferable to satisfy the condition expressed by the following formula (1).

E1×D1<E2×D2  (1)

A product of Young's modulus and thickness of a member is one of the indices representing hardness of the member. When this index satisfies the condition expressed by the above formula (1), the motion part of the structure 424 tends to flex more toward the first substrate 402 and flex less toward the second substrate 432. This is because the upper electrode 418 is harder than the above-mentioned laminate, and is less prone to expand or bend.

As mentioned earlier, the piezoelectric pump 470 of this embodiment transfers the fluid by the downward bend of the piezoelectric elements 420. Meanwhile, when the piezoelectric pump 470 is stopped, the structure 424 and the second substrate 432 are in contact with each other in the pump chamber 478, which makes it difficult for the piezoelectric elements 420 to bend upward. Hence a normal operation as a pump is difficult. Accordingly, by selecting the material and the thickness of each member so that the piezoelectric elements 420 satisfy the above formula (1), the piezoelectric pump 470 can operate more stably and transfer the fluid with greater stability.

Note that the above-mentioned Young's modulus can be measured by measuring Young's modulus of a sample by a surface elasticity method (e.g. by using a Young's modulus measurement system for ultrathin film by ALOtec), where the sample is obtained by forming a thin film with a thickness of 100 nm on a reference substrate having a known Young's modulus under conditions of a room temperature and 10⁻⁴ Pa. Here, in the case where the thin film is a laminate, the measurement is performed with the same thickness ratio as the thickness ratio of each member of the laminate constituting the piezoelectric element.

Moreover, in the piezoelectric pump 470 of this embodiment, it is preferable that each piezoelectric element 420 further includes a hard layer (not illustrated) on the second substrate 432 side of the upper electrode 418. A material and a thickness of the hard layer are set so that the above-mentioned laminate (first laminate) composed of the lower electrode 414 and the piezoelectric body 416 has a smaller product of Young's modulus and thickness than a laminate (second laminate) composed of the upper electrode 418 and the hard layer. In other words, when the Young's modulus of the first laminate is denoted by E1 (N/m²), the thickness of the first laminate is denoted by D1 (nm), the Young's modulus of the second laminate is denoted by E3 (N/m²), and the thickness of the second laminate is denoted by D3 (nm), it is preferable to satisfy the condition expressed by the following formula (2).

E1×D1<E3×D3  (2)

When the condition expressed by the above formula (2) is satisfied, the motion part of the structure 424 tends to flex more toward the first substrate 402 and flex less toward the second substrate 432. This is because the second laminate is harder than the first laminate and therefore is less prone to expand or bend. When the piezoelectric elements 420 satisfy the above formula (2), the piezoelectric pump 470 can operate more stably and transfer the fluid with greater stability. To reliably satisfy the above formula (2), the hard layer is preferably made of at least one metal selected from the group consisting of chromium (Cr; Young's modulus derived in the above-mentioned manner (the same applies hereafter)=248 N/m²), tungsten (W; 345 N/m²), tantalum (Ta; 186 N/m²), and platinum (Pt; 152 N/m²).

The hard layer can be obtained by further forming a layer of a material of the hard layer on the surface of the upper electrode layer 408 by, for example, sputtering, CVD, or vapor deposition in the step (A1), and patterning the formed layer together with the lower electrode layer 404, the piezoelectric body layer 406, and the upper electrode layer 408 in the step (A2).

The following describes a piezoelectric pump of a fourth embodiment of the present invention. FIG. 12 is a perspective top view schematically showing the piezoelectric pump of the fourth embodiment. FIG. 13 is a schematic view showing an operation of the piezoelectric pump of the fourth embodiment, where (A) schematically shows a cross section taken along the line in FIG. 12. FIG. 14 is a partially enlarged schematic sectional view showing the piezoelectric pump of the fourth embodiment. A piezoelectric pump 600 of the fourth embodiment includes: a structure 620 including six piezoelectric elements 602, 604, 606, 608, 610, and 612 (collectively written as “602 to 612”, the same applies hereafter) arranged along a flow direction of a fluid (the direction of the arrow A in FIG. 12) and one support member 614 that supports these piezoelectric elements 602 to 612; and a first substrate 622 and a second substrate 624 that sandwich the structure 620, and has: a pump chamber 630 surrounded by the second substrate 624 and the structure 620; and a first opening 650 and a second opening 652 that are communicated with the pump chamber 630 at the time of operation. Moreover, the piezoelectric elements 602 to 612 respectively include displacement parts 602 c to 612 c that are displaced by application of a voltage, and fixed parts 602 d to 612 d and 602 e to 612 e that are fixed by being sandwiched between the first substrate 622 and the second substrate 624. Further, from a state where the first substrate 622 is joined to the structure 620, a part of the first substrate 622 facing the displacement parts 602 c to 612 c and a surrounding part 614 a of the support member 614 surrounding the periphery of each of the displacement parts 602 c to 612 c is removed by etching, so as to expose the displacement parts 602 c to 612 c and the surrounding part 614 a. This forms an opening 622 a. The above-mentioned displacement parts 602 c to 612 c and surrounding part 614 a constitute a motion part of the structure 620.

In more detail, the structure 620 included in the piezoelectric pump 600 of this embodiment includes the six piezoelectric elements 602 to 612, and the single support member 614 that is directly joined to these piezoelectric elements 602 to 612 to support the piezoelectric elements 602 to 612. The support member 614 is a thin film that is made of a material such as a resin and has a thickness of 1.0 μm to 10 μm, as an example. A part 614 a of one main surface (upper surface) of the support member 614 facing the pump chamber 630 has a planar shape like a string of beads where six circular surfaces put in a row are partially overlapped with each other at their peripheries.

The piezoelectric elements 602 to 612 are in thin film form with a thickness of 0.5 μm to 10.0 μm as an example, and have circular main surfaces. As shown in FIG. 14, the piezoelectric elements 602 to 612 respectively include lower electrodes 602 a to 612 a (the lower electrodes 610 a and 612 a included respectively in the piezoelectric elements 610 and 612 are not illustrated), piezoelectric bodies 602 b to 612 b (the piezoelectric bodies 610 b and 612 b included respectively in the piezoelectric elements 610 and 612 are not illustrated), and upper electrodes 602 c to 612 c (the upper electrodes 610 c and 612 c included respectively in the piezoelectric elements 610 and 612 are not illustrated) which are laminated in this order. The piezoelectric elements 602 to 612 are embedded in the support member 614 in a state where the respective lower electrodes 602 a to 612 a are exposed to the opening 622 a. The piezoelectric elements 602 to 612 are not in direct contact with each other, and a lower surface of the support member 614 is exposed between the piezoelectric elements 602 to 612.

The first substrate 622 has the opening 622 a so as to expose a lower surface of the motion part of the structure 620, and also is joined to a part of the structure 620 other than the motion part. Here, the part of the structure 620 joined to the first substrate 622 is the lower surface of the support member 614. Meanwhile, a part of a lower surface of the second substrate 624 is joined to a part of an upper surface of the support member 614. In this way, the structure 620 including the support member 614 is fixed by being sandwiched between the first substrate 622 and the second substrate 624.

The second substrate is in contact with the upper surface of the motion part of the structure 620 when the piezoelectric pump is stopped, but is not joined to the upper surface of the motion part of the structure 620. The second substrate 624 has the first opening 650 and the second opening 652 passing through in its thickness direction, and these openings can be communicated with the pump chamber 630 when the piezoelectric pump 600 is in operation. The pump chamber 630 has partial pump chambers 632, 634, 636, 638, 640, and 642 respectively for the piezoelectric elements 602 to 612.

The protruded wires 602 d to 612 d are led out respectively from the lower electrodes 602 a to 612 a included in the six piezoelectric elements 602 to 612 in units of two wires, and the protruded wires 602 e to 612 e are led out respectively from the upper electrodes 602 c to 612 c included in the six piezoelectric elements 602 to 612 in units of one wire. As noted earlier, these wires are also the fixed parts 602 d to 612 d and 602 e to 612 e. These led-out wires 602 d to 612 d and 602 e to 612 e extend to terminals 660, and are connected to a power supply (not illustrated) via the terminals 660. Here, connection parts between the pair of electrodes and the corresponding wires are arranged in an order of the connection part between the lower electrode and the wire, the connection part between the upper electrode and the wire, and the connection part between the lower electrode and the wire, along the fluid flow direction from upstream. For example, in the case of connection parts 602 f and 602 h between the lower electrode 602 a and the two wires 602 d and a connection part 602 g between the upper electrode 602 c and the wire 602 e, the connection parts 602 f, 602 g, and 602 h are arranged in this order along the fluid flow direction from upstream. The same applies to the other connection parts (604 f to 604 h, 606 f to 606 h, 608 f to 608 h, 610 f to 610 h, and 612 f to 612 h).

For instance, such a piezoelectric pump 600 is manufactured in the following manner.

First, the lower electrodes 602 a to 612 a respectively including the protruded wires 602 d to 612 d, the piezoelectric bodies 602 b to 612 b, and the upper electrodes 602 c to 612 c respectively including the protruded wires 602 e to 612 e are laminated on the first substrate 622 which also functions as a film formation substrate, in this order. In more detail, first a layer for forming the lower electrodes 602 a to 612 a is formed on a surface of the first substrate 622 by, for example, sputtering, CVD, or vapor deposition. The first substrate 622 is not specifically limited so long as the layer for forming the lower electrodes 602 a to 612 a can be formed on its surface, and may be a substrate used for normal thin film formation. Preferably, the first substrate 622 is a Si substrate. A material of the layer for forming the lower electrodes 602 a to 612 a is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The layer for forming the lower electrodes 602 a to 612 a has a thickness of 0.05 μm to 1.0 μm, as an example.

Next, the layer for forming the lower electrodes 602 a to 612 a is patterned to a desired shape. A method of the patterning is not specifically limited. As an example, after forming a mask resist on a surface of the layer for forming the lower electrodes as an etch mask, a part of the layer not covered by the mask resist is removed by etching, and then the mask resist is removed. As a result, the lower electrodes 602 a to 612 a are obtained.

Next, the piezoelectric bodies 602 b to 612 b are formed on surfaces of the lower electrodes 602 a to 612 a (excluding surfaces of the wires 602 d to 612 d). A method of forming the piezoelectric bodies 602 b to 612 b may be sputtering, CVD, or vapor deposition. A material of the piezoelectric bodies 602 b to 612 b is not specifically limited so long as it is a piezoelectric material capable of thin film formation. For example, PZT, barium titanate, and the like are applicable. PZT (lead zirconate titanate) is particularly preferable as it has excellent piezoelectric properties and also is easily available. The piezoelectric bodies 602 b to 612 b have a thickness of 0.5 μm to 5.0 μm, as an example.

Following this, the upper electrodes 602 c to 612 c are formed on surfaces of the piezoelectric bodies 602 b to 612 b by, for example, sputtering, CVD, or vapor deposition. A material of the upper electrodes 602 c to 612 c is not specifically limited so long as it is usable as an electrode material of a piezoelectric element. For example, platinum, gold, copper, and an alloy including these metals are applicable. The upper electrodes 602 c to 612 c have a thickness of 0.05 μm to 1.0 μm, as an example.

For instance, the piezoelectric bodies 602 b to 612 b and the upper electrodes 602 c to 612 c may be formed in such a manner that, after forming a resist of a predetermined shape on the lower electrodes 602 a to 612 a, the piezoelectric bodies 602 b to 612 b and the upper electrodes 602 c to 612 c are formed in this order, and then the resist is removed. Thus, the piezoelectric elements 602 to 612 in which the lower electrodes 602 a to 612 a, the piezoelectric bodies 602 b to 612 b, and the upper electrodes 602 c to 612 c are laminated on the first substrate 622 in this order is obtained.

Next, a layer for forming the support member 614 is formed so as to cover the piezoelectric elements 602 to 612.

A material of this layer is an insulating material, and preferably a flexible material since the layer needs to bend with the displacement of the piezoelectric bodies 602 b to 612 b without being damaged. When a flexible material is employed as the material of the layer for forming the support member 614, the displacement of the piezoelectric bodies 602 b to 612 b can be favorably transmitted to the pump chamber 630, which contributes to enhanced efficiency of the piezoelectric pump 600. In detail, the material of the layer for forming the support member 614 is preferably a resin material. In this case, first a resin composition (e.g. a mixture of a solvent and a resin and/or a monomer) which is a raw material of the resin material is applied onto the surfaces of the first substrate 622 and piezoelectric elements 602 to 612. The applied resin composition is then solidified by drying or the like or hardened by heating, optical irradiation, or the like. After this, the resin composition hardened according to need is patterned to a desired shape. The patterning may be performed using a known method of patterning a resin material. For example, a photolithography method is applicable. As the resin material, a material that favorably adheres to the film formation substrate and the piezoelectric elements 602 to 612 and also has favorable patterning properties such as developability is preferable. For example, a silicone resin, polyimide, parylene, and the like are applicable. Thus, the structure 620 including the piezoelectric elements 602 to 612 and the support member 614 formed on the film formation substrate is obtained.

Aside from the above-mentioned structure 620, the second substrate 624 is made. For instance, the second substrate 624 is obtained from a glass substrate or a ceramic substrate having a thickness of 0.2 mm to 2.0 mm. A surface of the substrate is processed (patterned) to a predetermined shape by etching or the like. Further, the first opening 650 and the second opening 652 are formed through the substrate in its thickness direction by etching or the like, at predetermined positions. In this way, the second substrate 624 that has the openings 650 and 652 and whose lower surface is patterned to the predetermined shape is obtained.

Next, the second substrate 624 is attached onto the above-mentioned structure 620. Here, having positioned the structure 620 and the second substrate 624 so as to make the patterned lower surface of the second substrate 624 face the surface of the structure 620 where the support member 614 is formed and also to form the pump chamber 630, the lower surface of the second substrate 624 and the support member 614 are joined by being attached to each other around an area corresponding to the pump chamber 630. Note here that the second substrate 624 is in contact with the surrounding part 614 a of the support member 614 and the displacement parts constituting the motion part, but is not joined to the surrounding part 614 a and the displacement parts 602 c to 612 c. A method of the attachment may be a method of applying, for example, an adhesive to an area of contact between the support member 614 and the second substrate 624. Subsequently, the first substrate 622 is partially etched. In detail, the part of the first substrate 622 facing the above-mentioned motion part is removed by etching, to form the opening 622 a. As a result, the surfaces of the displacement parts and surrounding part 614 a constituting the motion part are exposed. These parts can expand/contract and bend according to the displacement of the piezoelectric elements 602 to 612.

A method of the etching is not specifically limited. As an example, after forming a mask resist of a predetermined shape on a surface of the first substrate 622 as an etch mask, a part of the first substrate 622 not covered by the mask resist is removed by etching, and then the mask resist is removed. As an alternative etching method, a liftoff method of performing resist patterning, film formation, and unwanted part removal may be used. The etching is preferably dry etching. Examples include reactive gas etching, reactive ion etching, reactive ion beam etching, ion beam etching, and reactive laser beam etching.

Thus, the piezoelectric pump 600 of the fourth embodiment is obtained. As described above, the piezoelectric pump 600 of this embodiment is manufactured on the basis of the so-called thin film process. This makes it possible to suppress a variation in quality, enhance a yield, and reduce manufacturing costs.

The following describes a method of operating the piezoelectric pump 600 of this embodiment, with reference to FIG. 13. First, in a step (A), the piezoelectric pump 600 is in a stopped state, and the upper surface of the structure 620 is in contact with the second substrate 624. Accordingly, the first opening 650 and the second opening 652 are blocked by the support member 614 forming the pump chamber 630. Next, in a step (B), a voltage is applied between the lower electrode 602 a of the piezoelectric element 602 from the wire 602 d via the connection part 602 h and the upper electrode 602 c of the piezoelectric element 602 from the wire 602 e via the connection part 602 g, and at the same time a voltage is applied between the lower electrode 604 a of the piezoelectric element 604 from the wire 604 d via the connection part 604 f and the upper electrode 604 c of the piezoelectric element 604 from the wire 604 e via the connection part 604 g. As a result, the displacement of the piezoelectric bodies 602 b and 604 b causes the piezoelectric elements 602 and 604 to simultaneously bend downward together with the support member 614. With this bend, the support member 614 situated above and between the piezoelectric elements 602 and 604 is pulled downward, so that the support member 614 and the second substrate 624 separate from each other in these areas. This induces a negative pressure in the pump chambers 632 and 634, and accordingly the piezoelectric pump 600 sucks the fluid from the first opening 650 into these pump chambers 632 and 634. Note that the top of the bent piezoelectric element 602 is a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 602 h and the connection part 602 g than to a central part in the in-plane direction, and the top of the bent piezoelectric element 604 is a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 604 f and the connection part 604 g than to a central part in the in-plane direction.

Next, in a step (C), the voltage application between the lower electrode 602 a and the upper electrode 602 c is stopped, and a voltage is applied between the lower electrode 604 a of the piezoelectric element 604 from the wire 604 d via the connection part 604 h and the upper electrode 604 c of the piezoelectric element 604 from the wire 604 e via the connection part 604 g, and at the same time a voltage is applied between the lower electrode 606 a of the piezoelectric element 606 from the wire 606 d via the connection part 606 f and the upper electrode 606 c of the piezoelectric element 606 from the wire 606 e via the connection part 606 g. As a result, the piezoelectric element 602 returns to the stopped state and the structure 620 and the second substrate 624 come into direct contact again above and between the piezoelectric elements 602 and 604, while the displacement of the piezoelectric body 606 b causes the piezoelectric element 606 to bend downward together with the support member 614. With this bend, the support member 614 situated above and between the piezoelectric elements 604 and 606 is pulled downward, so that the structure 620 and the second substrate 624 separate in this area. This pressurizes the pump chamber 632 and also induces a negative pressure in the pump chamber 636, and accordingly the piezoelectric pump 600 pushes the fluid out of the pump chamber 632 while sucking the fluid into the pump chamber 636, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 604 a is switched from via the connection part 604 f to via the connection part 604 h, the top of the bent piezoelectric element 604 changes from the part that is slightly closer to the imaginary connection part at the intermediate point between the connection part 604 f and the connection part 604 g than to the central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 604 h and the connection part 604 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 604 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 634 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

Following this, in a step (D), the voltage application between the lower electrode 604 a and the upper electrode 604 c is stopped, and a voltage is applied between the lower electrode 606 a of the piezoelectric element 606 from the wire 606 d via the connection part 606 h and the upper electrode 606 c of the piezoelectric element 606 from the wire 606 e via the connection part 606 g, and at the same time a voltage is applied between the lower electrode 608 a of the piezoelectric element 608 from the wire 608 d via the connection part 608 f and the upper electrode 608 c of the piezoelectric element 608 from the wire 608 e via the connection part 608 g. As a result, the piezoelectric element 604 returns to the stopped state and the structure 620 and the second substrate 624 come into direct contact again above and between the piezoelectric elements 604 and 606, while the displacement of the piezoelectric body 608 b causes the piezoelectric element 608 to bend downward together with the support member 614. With this bend, the support member 614 situated above and between the piezoelectric elements 606 and 608 is pulled downward, so that the structure 620 and the second substrate 624 separate in this area. This pressurizes the pump chamber 634 and also induces a negative pressure in the pump chamber 638, and accordingly the piezoelectric pump 600 pushes the fluid out of the pump chamber 634 while sucking the fluid into the pump chamber 638, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 606 a is switched from via the connection part 606 f to via the connection part 606 h, the top of the bent piezoelectric element 606 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 606 f and the connection part 606 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 606 h and the connection part 606 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 606 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 636 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

Next, in a step (E), the voltage application between the lower electrode 606 a and the upper electrode 606 c is stopped, and a voltage is applied between the lower electrode 608 a of the piezoelectric element 608 from the wire 608 d via the connection part 608 h and the upper electrode 608 c of the piezoelectric element 608 from the wire 608 e via the connection part 608 g, and at the same time a voltage is applied between the lower electrode 610 a of the piezoelectric element 610 from the wire 610 d via the connection part 610 f and the upper electrode 610 c of the piezoelectric element 610 from the wire 610 e via the connection part 610 g. As a result, the piezoelectric element 606 returns to the stopped state and the structure 620 and the second substrate 624 come into direct contact again above and between the piezoelectric elements 606 and 608, while the displacement of the piezoelectric body 610 b causes the piezoelectric element 610 to bend downward together with the support member 614. With this bend, the support member 614 situated above and between the piezoelectric elements 608 and 610 is pulled downward, so that the structure 620 and the second substrate 624 separate in this area. This pressurizes the pump chamber 636 and also induces a negative pressure in the pump chamber 640, and accordingly the piezoelectric pump 600 pushes the fluid out of the pump chamber 636 while sucking the fluid into the pump chamber 640, thereby transferring the fluid more downstream. Moreover, because the voltage application to the lower electrode 608 a is switched from via the connection part 608 f to via the connection part 608 h, the top of the bent piezoelectric element 608 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 608 f and the connection part 608 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 608 h and the connection part 608 g than to the central part in the in-plane direction. That is, the top of the bent piezoelectric element 608 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 638 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

After this, in a step (F), the voltage application between the lower electrode 608 a and the upper electrode 608 c is stopped, and a voltage is applied between the lower electrode 610 a of the piezoelectric element 610 from the wire 610 d via the connection part 610 h and the upper electrode 610 c of the piezoelectric element 610 from the wire 610 e via the connection part 610 g, and at the same time a voltage is applied between the lower electrode 612 a of the piezoelectric element 612 from the wire 612 d via the connection part 612 f and the upper electrode 612 c of the piezoelectric element 612 from the wire 612 e via the connection part 612 g. As a result, the piezoelectric element 608 returns to the stopped state and the structure 620 and the second substrate 624 come into direct contact again above and between the piezoelectric elements 608 and 610, while the displacement of the piezoelectric body 612 b causes the piezoelectric element 612 to bend downward together with the support member 614. With this bend, the support member 614 situated above and between the piezoelectric elements 610 and 612 is pulled downward, so that the structure 620 and the second substrate 624 separate in this area. This pressurizes the pump chamber 638 and also induces a negative pressure in the pump chamber 642, and accordingly the piezoelectric pump 600 pushes the fluid out of the pump chamber 638 while sucking the fluid into the pump chamber 642, thereby discharging the fluid from the second opening 652. Moreover, because the voltage application to the lower electrode 610 a is switched from via the connection part 610 f to via the connection part 610 h, the top of the bent piezoelectric element 610 changes from a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 610 f and the connection part 610 g than to a central part in the in-plane direction, to a part that is slightly closer to an imaginary connection part at an intermediate point between the connection part 610 h and the connection part 610 g than the central part in the in-plane direction. That is, the top of the bent piezoelectric element 610 moves downstream in the fluid flow direction. This causes the fluid in the pump chamber 640 to be pushed downstream, which further facilitates the transfer of the fluid downstream.

By repeating the steps described above, it is possible to transfer the fluid through the piezoelectric pump 600 of this embodiment. In this case, for example the above-mentioned step (B) may be started at the same time as the start of the above-mentioned step (E). By doing so, the fluid transferring amount per unit time by the piezoelectric pump 600 can be further increased.

The piezoelectric pump 600 of the fourth embodiment has the similar construction and operation as the piezoelectric pump 470 of the third embodiment, and therefore can achieve the same effects as the piezoelectric pump 470. In addition, the piezoelectric pump 600 of the fourth embodiment can achieve the following effects. That is, by arranging the connection parts between the electrodes and the wires in the above-mentioned manner, the piezoelectric pump 600 of this embodiment can move the top of one bent piezoelectric element downstream. Thus, in the piezoelectric pump of the fourth embodiment, the fluid is transferred not only by a peristaltic motion of the plurality of piezoelectric elements 602 to 612 as a whole but also by a peristaltic motion within each individual piezoelectric element. Since the transfer of the fluid downstream is facilitated in this way, the applied voltage can be converted to the fluid transferring amount more efficiently.

Although the best mode for carrying out the present invention has been described above, the present invention is not limited to the above embodiments. Various changes can be made to the present invention without departing from the scope of the invention. For example, the planar shapes of the piezoelectric element and the support member included in the piezoelectric pump according to the present invention or the piezoelectric pump unit according to the present invention may be those shown in FIG. 5. FIG. 5 is a schematic view showing the planar shapes of the piezoelectric element and the support member. FIG. 5B shows a piezoelectric element 506 and a support member 508 having the same shapes as the first piezoelectric element 308 and the first support member 310 in the embodiment described above. For example, a piezoelectric element 502 may have a shape with no constriction, as shown in FIG. 5A. Alternatively, a piezoelectric element 510 may have a shape whose constriction is gradually tapered toward an electrode lead-out part in its in-plane direction, and a support member 512 may have a constriction, as shown in FIG. 5C. A piezoelectric element 514 and/or a support member 516 may be circular in shape, as shown in FIG. 5D. Moreover, though not illustrated, it is also possible to provide a constriction only in the support member, with no constriction being provided in the piezoelectric element. In such a case, too, a large flow amount can be realized with application of a small voltage. Furthermore, the piezoelectric element or the support member may have a constriction in its thickness direction, in addition to or instead of its in-plane direction. In this way, a large flow amount can be realized with application of a small voltage. Moreover, the shape of the constriction may be changed appropriately in order to control the displacement in the in-plane direction and the displacement in the thickness direction in a well balanced manner, according to the type of the fluid transferred.

Moreover, in the piezoelectric pump of the first embodiment, the support member may be joined only to a part or whole of the periphery of the piezoelectric element or an edge face of the piezoelectric element. As an alternative, the support member may be joined so as to cover the surface of the piezoelectric element on the void side. In such cases, the piezoelectric element is exposed to the pump chamber, and so is in direct contact with the fluid. The support member may instead be joined so as to cover both surfaces of the piezoelectric element on the void side and the pump chamber (flow path) side.

Though the second embodiment describes the case where six piezoelectric elements are disposed on one support member, this is not a limit for the present invention, which can be realized so long as two or more piezoelectric elements, that is, a plurality of piezoelectric elements, are disposed on one support member to achieve a peristaltic motion. For instance, two piezoelectric elements may be disposed. Moreover, though the second embodiment describes the case where a voltage is simultaneously applied to two piezoelectric elements in the operation method of the piezoelectric pump, the voltage application may be performed on one piezoelectric element at a time, or simultaneously performed on three or more piezoelectric elements. In this case, the voltage application can be started sequentially from the upstream piezoelectric element.

The second embodiment describes the case where the support member is a continuous film formed in the same step, but a plurality of members formed in separate steps may be joined as one support member. Moreover, the second embodiment describes the case where one inner wall surface of the pump chamber is bent by the displacement of the piezoelectric element. Here, in view of suppressing dead spaces in the pump chamber, it is preferable that the piezoelectric element occupies a large area of the bent inner wall surface. For example, the area occupied by the piezoelectric element is preferably at least 50%, more preferably at least 80%, further preferably at least 90%, especially preferably at least 95%, and extremely preferably at least 98%. Note however that, when the area occupied by the piezoelectric element exceeds 100%, the vibration of the piezoelectric element is suppressed and the displacement is reduced. Therefore, the area occupied by the piezoelectric element is preferably no more than 100%.

Furthermore, the main surface shape of the piezoelectric element and the main surface shape of the part of the support member facing the pump chamber are not limited to those described above. To efficiently convert the radial displacement of the piezoelectric element to the bend, it is desirable that the main surface shape of the piezoelectric element and the main surface shape of the corresponding part of the support member are circular. However, the main surfaces may instead be, for example, an ellipse or a polygon such as a rectangle. Moreover, the connection parts between the electrodes and the wires are not limited to the above-mentioned arrangement. As an example, one connection part may be provided for each of the lower electrode and the upper electrode.

Moreover, instead of the third or fourth embodiment, the piezoelectric pump may have only one piezoelectric element. FIG. 17 schematically shows an example of such a piezoelectric pump which is in a state of operation. A piezoelectric pump 900 shown in FIG. 17 includes: a structure 920 including one piezoelectric element 902 and one support member 914 that supports the piezoelectric element 902; and a first substrate 922 and a second substrate 924 that sandwich the structure 920, and has: a pump chamber 930 surrounded by the second substrate 924 and the structure 920; and a first opening 950 and a second opening 952 that are communicated with the pump chamber 930 at the time of operation. The piezoelectric element 902 includes a displacement part that is displaced by application of a voltage, and a fixed part that is fixed by being sandwiched between the first substrate 922 and the second substrate 924. Further, from a state where the first substrate 922 is joined to the structure 920, a part of the first substrate 922 facing the displacement part of the piezoelectric element 902 and a surrounding part of the support member 914 surrounding the periphery of the displacement part is removed by etching, so as to expose the displacement part and surrounding part. This forms an opening 922 a. The above-mentioned displacement part, fixed part, and surrounding part may have the same construction and arrangement as in the case of one piezoelectric element in the fourth embodiment. By arranging the connection parts between the electrodes and the wires in the same way as the fourth embodiment, the piezoelectric element 902 can move in a peristaltic manner like one of the plurality of piezoelectric elements in the fourth embodiment. Hence the fluid can be transferred efficiently. In FIG. 17, the upstream opening 950 and the pump chamber 930 are communicated with each other, whilst the downstream opening 952 is blocked by the structure 920. By this state, the piezoelectric pump 900 can suck the fluid from outside. Moreover, the third and fourth embodiments describe the case where, when the piezoelectric pump is stopped, the structure and the second substrate are in contact with each other and there is almost no space in the pump chamber. Alternatively, a space may be provided in the pump chamber between the structure and the second substrate even when the piezoelectric pump is stopped. To provide such a space, a resin for bonding the structure and the second substrate may be applied between the structure and the second substrate with an appropriate thickness, or a substrate may be further provided between the structure and the second substrate.

EXAMPLES

The following describes the present invention in more detail by way of examples, though the present invention is not limited to these examples.

(Effect Verification Test Based on Differences in First Substrate Making Method)

In this test, to verify the displacement amount of the piezoelectric element in the piezoelectric pump, samples shown in FIGS. 15A and 15B were made. First, the making of the sample shown in FIG. 15A according to an example was started by laminating a lower electrode layer (not illustrated, Pt as a material, 0.1 μm in thickness), a piezoelectric body layer (not illustrated, PZT as a material, 2 μm to 2.5 μm in thickness), and an upper electrode layer (not illustrated, Pt as a material, 0.1 μm in thickness) on a Si substrate of 400 μm in thickness by vapor deposition and sputtering, in this order. Next, the lower electrode layer, the piezoelectric body layer, and the upper electrode layer were patterned to a planar shape shown in FIG. 15C by ion milling and etching, to obtain a piezoelectric element. Next, an insulating polyimide resin was applied onto the Si substrate and the piezoelectric element as a support member for the piezoelectric element, and the entire structure was heated at 280° C. for one hour, thereby hardening the polyimide resin.

Further, the same polyimide resin was applied to the periphery of the support member for bonding and space formation, and a glass substrate was placed thereon without heating. After this, the entire structure was heated at 280° C. for one hour to harden the polyimide resin for bonding, thereby joining the support member and the glass substrate via the polyimide resin. A part of the Si substrate was then etched from the rear by reactive ion etching using Deep-RIE, as a result of which the sample of the example was obtained. Note here that the Si substrate was etched so as to form an opening having a planar shape shown in FIG. 15C.

On the other hand, the making of the sample shown in FIG. 15B according to a comparative example was started by laminating a lower electrode layer (not illustrated, Pt as a material, 0.1 μm in thickness), a piezoelectric body layer (not illustrated, PZT as a material, 2 μm to 2.5 μm in thickness), and an upper electrode layer (not illustrated, Pt as a material, 0.1 μm in thickness) on a Si substrate for formation by vapor deposition and sputtering, in this order. Next, the lower electrode layer, the piezoelectric body layer, and the upper electrode layer were patterned to the planar shape shown in FIG. 15C by ion milling and etching, to obtain a piezoelectric element. Next, an insulating polyimide resin was applied onto the Si substrate and the piezoelectric element as a support member for the piezoelectric element, and the entire structure was heated at 280° C. for one hour, thereby hardening the polyimide resin.

Further, the same polyimide resin was applied to the periphery of the support member for bonding and space formation, and a glass substrate was placed thereon without heating. After this, the entire structure was heated at 280° C. for one hour to harden the polyimide resin for bonding, thereby joining the support member and the glass substrate via the polyimide resin. The entire Si substrate for formation was then etched from the rear by hydrofluoric acid etching. After this, a glass substrate having an opening of the planar shape shown in FIG. 15C was joined to the surface of the structure composed of the piezoelectric element and the support member that is entirely exposed as a result of etching the Si substrate, by film transfer. Thus, the sample of the comparative example was obtained.

A voltage (driving voltage=0 V to 10 V, driving frequency=10 Hz) was applied to the piezoelectric elements of the obtained samples, and the (maximum) amount of displacement in the thickness direction according to the bend of the structure composed of the piezoelectric element and the support member was measured. A laser Doppler vibrometer by Polytec was used as an evaluation machine. Results are shown in Table 1.

TABLE 1 Example Comparative Example Displacement amount (nm) 5400 742 Displacement amount (nm/V) 540 74.2

From these results, it was observed that the sample of the example exhibits a larger displacement amount of the structure composed of the piezoelectric element and the support member, than the sample of the comparative example.

(Effect Verification Test on Hard Layer)

Next, the following test was conducted to verify the effects of the hard layer. First, samples were made in the same manner as the making method of the sample shown in FIG. 15A in the above “effect verification test based on differences in first substrate making method”, except that a hard layer (not illustrated) with various thicknesses was further formed on the upper electrode layer by sputtering. Note that the samples in this test were obtained with the hard layer made of chromium (Cr) or titanium (Ti; Young's modulus=116 N/m²).

A voltage (driving voltage=0 V to 10 V, driving frequency=10 Hz) was applied to the piezoelectric elements of the obtained samples so that the piezoelectric body flexes upward (toward the glass substrate). A contact area between the structure and the glass substrate at this time was measured by image analysis. Results are shown in FIG. 16.

From these results, it was observed that, when chromium is used as the material of the hard layer, the upward flex is reduced as the thickness of the hard layer increases, so that the piezoelectric pump can transfer the fluid stably. On the other hand, when titanium is used as the material of the hard layer, the upward flex is not reduced much even when the thickness of the hard layer increases, so that the piezoelectric pump cannot transfer the fluid stably when compared with the case of using chromium as the material of the hard layer.

The piezoelectric pump and the fluid transferring system according to the present invention can be applied to various apparatuses for transferring fluids. Examples of such fluids include a liquid such as a liquid reagent used for micro chemical reaction or ink of a high-resolution printer, and a gas such as test gas of a gas chromatograph or reactive gas in a fuel cell. For instance, the piezoelectric pump and the fluid transferring system according to the present invention can be included in a fine filter apparatus or a fluid supply apparatus to a gas sensor. 

1. A piezoelectric pump comprising: a structure including a piezoelectric element and a support member that supports the piezoelectric element; and a first substrate and a second substrate that sandwich said structure, wherein the piezoelectric pump has: a pump chamber surrounded by said second substrate and said structure; and a first opening and a second opening that are communicated with said pump chamber, and wherein a space is provided so that said structure flexes in a direction opposite to said pump chamber according to an operation of the piezoelectric element.
 2. The piezoelectric pump according to claim 1, wherein the piezoelectric pump has a void surrounded by said first substrate and said structure.
 3. The piezoelectric pump according to claim 2, wherein at least one of said piezoelectric element and said support member has a constriction in at least one of an in-plane direction and a thickness direction of said piezoelectric element.
 4. The piezoelectric pump according to claim 1, wherein said structure includes two or more piezoelectric elements arranged in a flow direction of a fluid, and one support member that supports said two or more piezoelectric elements, and wherein the piezoelectric pump has a void surrounded by said first substrate and said structure.
 5. The piezoelectric pump according to claim 4, wherein said support member is a thin film, a part of a main surface of said support member facing said pump chamber having a planar shape in which two or more circular surfaces are partially overlapped with each other, and wherein each of said two or more piezoelectric elements is a thin film that is supported on the two or more circular surfaces and has a circular main surface.
 6. The piezoelectric pump according to claim 4, wherein each of said two or more piezoelectric elements includes a piezoelectric body and one pair of electrodes sandwiching said piezoelectric body, and has three or more wires led out alternately from said pair of electrodes along the flow direction of the fluid.
 7. The piezoelectric pump according to claim 1, wherein said piezoelectric element includes a displacement part that is displaced by application of a voltage, and a fixed part that is fixed by being directly or indirectly sandwiched between said first substrate and said second substrate, and wherein from a state where said first substrate is joined to said structure, a part of said first substrate facing said displacement part and a surrounding part of said support member surrounding a periphery of said displacement part is removed so as to expose said displacement part and said surrounding part.
 8. The piezoelectric pump according to claim 7, wherein said piezoelectric element includes a first electrode, a piezoelectric body, and a second electrode that are laminated in the stated order in a direction from said first substrate to said second substrate, and wherein a first laminate composed of said first electrode and said piezoelectric body has a smaller product of Young's modulus and thickness than said second electrode.
 9. The piezoelectric pump according to claim 8, wherein said piezoelectric element further includes a hard layer on a surface of said second electrode facing said second substrate, and wherein said first laminate has a smaller product of Young's modulus and thickness than a second laminate composed of said second electrode and said hard layer.
 10. The piezoelectric pump according to claim 9, wherein said hard layer is made of at least one metal selected from the group consisting of chromium, tungsten, tantalum, and platinum.
 11. A fluid transferring system comprising a first valve unit, a piezoelectric pump unit, and a second valve unit in the stated order along a flow direction of a fluid, wherein said piezoelectric pump unit includes: a first structure including a first piezoelectric element and a first support member that supports said first piezoelectric element; and a first substrate and a second substrate that sandwich said first structure, said piezoelectric pump unit has: a pump chamber surrounded by said second substrate and said first structure; and a first opening and a second opening that are communicated with said pump chamber, and a space is provided so that said first structure flexes in a direction opposite to said pump chamber according to an operation of said first piezoelectric element, wherein said first valve unit includes: a second structure including a second piezoelectric element and a second support member that supports said second piezoelectric element; and said first substrate and said second substrate that sandwich said second structure, and said first valve unit is opened or closed by a part of said second structure becoming out of or into contact with a part of said first substrate or said second substrate according to an operation of said second piezoelectric element, and wherein said second valve unit includes: a third structure including a third piezoelectric element and a third support member that supports said third piezoelectric element; and said first substrate and said second substrate that sandwich said third structure, and said second valve unit is opened or closed by a part of said third structure becoming out of or into contact with a part of said first substrate or said second substrate according to an operation of said third piezoelectric element. 